@mikael Thanks for your reactivity !

@mikael , I regularly use your modules and I thank you for it. Unfortunately, since the last version of ui3, I have an error when I want to use it.
Here is the Traceback :

Traceback (most recent call last):
  File "/private/var/mobile/Library/Mobile Documents/iCloud~com~omz-software~Pythonista3/Documents/ui3-master/sheet.py", line 7, in <module>
    from ui3.anchor import *
  File "/private/var/mobile/Library/Mobile Documents/iCloud~com~omz-software~Pythonista3/Documents/ui3-master/ui3/__init__.py", line 12, in <module>
    from ui3.anchor import *
  File "/private/var/mobile/Library/Mobile Documents/iCloud~com~omz-software~Pythonista3/Documents/ui3-master/ui3/anchor/__init__.py", line 821, in <module>
    via_screen,
NameError: name 'via_screen' is not defined ```

@cvp Thanks a lot ! I’m happy to see that I progress slowly…
I had found textView().becomeFirstResponder() but couldn’t find to witch element it had to be applied. The _get_editor_tab is not documented ! To find it, do you open editor.py in the site-packages of Standard Library ?
It's very instructive 🤓, I'm going to end up managing on my own. 😉

@cvp I learn a lot adapting your scripts to my needs !
You will find after this message my/your script to add a keyboard icon in the titlebar to call my script to add my special key row to the keyboard.
The system is rather practical, but to make the handling as transparent as possible : when I add my key row, I hide the keyboard with tv.endEditing(True), and I would like to make it reappear with my special key row : but I’ve not found a command as simple as tv.startEditing 🙁 ; it’s perharps possible to simulate a touch in the TextView, but I neither can’t find a solution to do it 🥶
After several hours of searching, I throw in the towel and ask for help…🥵

from objc_util import *
import ui
from ui3.sfsymbol import *

w = ObjCClass('UIApplication').sharedApplication().keyWindow()
main_view = w.rootViewController().view()

def get_toolbar(view):
    # get main editor toolbar, by recursively walking the view
    sv = view.subviews()
    for v in sv:
        if v._get_objc_classname().startswith(b'OMTabViewToolbar'):
            return v
        tb = get_toolbar(v)
        if tb:
            return tb
            
# ———————————————————————————————————————————————————————————————————

def keyboard_btn_action(sender):
    
    def run_script(scriptPath):
        import os
        from objc_util import ObjCInstance,ObjCClass
    
        dir = os.path.expanduser(scriptPath)
        I3=ObjCClass('PYK3Interpreter').sharedInterpreter()
        I3.runScriptAtPath_argv_resetEnvironment_(dir, [''], True)

    iCloudPath = "/private/var/mobile/Library/Mobile Documents/iCloud~com~omz-software~Pythonista3/Documents/"
    iPadPath = '~/Documents/'
    scriptPath = 'PROJETS/KEYBOARD/my_special_key_row.py'
    run_script(iCloudPath + scriptPath)
            
# ———————————————————————————————————————————————————————————————————

def create_keyboard_button(action,index=0):
    global __persistent_views
    
    assert(callable(action))
    tb = get_toolbar(main_view)
        
    try:
        __persistent_views
    except NameError:
        __persistent_views={}
        
    #check for existing button in this index and delete if needed
    remove_toolbar_button(index)    
    btn = ui.Button()
    btn.frame = (110, 24, 40, 40)
    
    if ui.get_ui_style() == 'dark':
        btn.tint_color = 'white' 
    else:
        btn.tint_color = '#0D89B5' 
    btn.image = SymbolImage('keyboard', point_size=14, weight=THIN, scale=SMALL)
    btn.image = btn.image.with_rendering_mode(ui.RENDERING_MODE_AUTOMATIC)
            
    btn.action=action
    btn_obj=ObjCInstance(btn)
    __persistent_views[index]=(btn,action)
    tb.superview().superview().addSubview_(btn_obj) # in front of all buttons
    
    return btn
    
# ———————————————————————————————————————————————————————————————————
    
def remove_toolbar_button(index):
    global __persistent_views
    
    try:
        btn,action = __persistent_views.pop(index)
        btn.action= None
        ObjCInstance(btn).removeFromSuperview()
    except KeyError:
        pass

# ===================================================================

#if __name__=='__main__': # if imported by pythonista startup   
        
create_keyboard_button(keyboard_btn_action) 
        
create_keyboard_button(keyboard_btn_action)

Here is my scrolling special key row to replace the standard one.
This script is a mix between @cvpe's script AddButtonsToPythonistaKeyboard https://github.com/cvpe/Pythonista-scripts/blob/master/AddButtonsToPythonistaKeyboard.py
and my own work.
It uses module ui3.sfsymbol of @mikaelho https://github.com/mikaelho/ui3
Thanks for all their work for Pythonista's community.
It certainly contains errors as I am not an expert coder like the majority of you but it does work for me 😉
Feel free to improve and adapt it to your needs!

# =================================================================
# This script is a mix between @cvpe's script AddButtonsToPythonistaKeyboard 
# https://github.com/cvpe/Pythonista-scripts/blob/master/AddButtonsToPythonistaKeyboard.py
# and my own work.
# It uses module ui3.sfsymbol of @mikaelho
# https://github.com/mikaelho/ui3
# 
# enez.houad@free.fr
# =================================================================

import ui, editor, clipboard
from objc_util import *
from ui3.sfsymbol import *

@on_main_thread
def tv_find(tv):
    import console, re
    
    tv.find = console.input_alert('Expression à rechercher :', '', tv.find, hide_cancel_button=True)
    txt = tv.find
    
    for sv in tv.subviews():
        if 'SUIButton_PY3' in str(sv._get_objc_classname()):
            sv.removeFromSuperview()
    if txt == '':
        return
    t = str(tv.text())
    
    for m in re.finditer(txt, t):
        st,en = m.span()
        p1 = tv.positionFromPosition_offset_(tv.beginningOfDocument(), st)
        p2 = tv.positionFromPosition_offset_(tv.beginningOfDocument(), en)
        rge = tv.textRangeFromPosition_toPosition_(p1,p2)
        rect = tv.firstRectForRange_(rge)
        x,y = rect.origin.x,rect.origin.y
        w,h = rect.size.width,rect.size.height
        
        l = ui.Button()
        l.frame = (x,y,w,h)
        if '|' not in txt:
            l.background_color = (1,0,0,0.2)
        else:
            # search multiple strings
            wrds = txt.split('|')
            idx = wrds.index(t[st:en])
            cols = [(1,0,0,0.2), (0,1,0,0.2), (0,0,1,0.2), (1,1,0,0.2), (1,0,1,0.2), (0,1,1,0.2)]
            col = cols[idx % len(cols)]
            l.background_color = col
        l.corner_radius = 4
        l.border_width = 1
        tv.addSubview_(l)       
    
# ———————————————————————————————————————————————————————————————————

def key_pressed(sender):
    
    tv = sender.objc_instance.firstResponder() # associated TextView  
    
    cursor = tv.offsetFromPosition_toPosition_(tv.beginningOfDocument(),     tv.selectedTextRange().start()) # get actual cursor position

    if sender.name == 'tab':
        tv.insertText_('\t')
    
    elif sender.name == 'paste':
        tv.insertText_(clipboard.get()) 
        
    elif sender.name == 'undo':
        tv.undoManager().undo()
        
    elif sender.name == 'redo':
        tv.undoManager().redo()
    
    elif sender.name == 'del_right':
        # delete at right = delete at left of next
        if cursor == (len(str(tv.text()))-1): # already after last character
            return
        cursor_position = tv.positionFromPosition_offset_(tv.beginningOfDocument(), cursor+1)
        tv.selectedTextRange = tv.textRangeFromPosition_toPosition_(cursor_position, cursor_position)
        tv.deleteBackward()     
        
    elif sender.name == 'find':
        tv_find(tv)
        
    elif sender.name == 'line-':
        tv.insertText_('# ' + 65 * '—')
    elif sender.name == 'line=':
        tv.insertText_('# ' + 65 * '=')
    elif sender.name == 'line#':
        tv.insertText_(67 * '#')
        
    else: # all other keys > insert button title
        tv.insertText_(sender.title)
    
# ===================================================================
    
class SpecialKeyRow(ui.View):
    
    def __init__(self, pad, *args, **kwargs):
        
        self.pad = pad
    
        sw, sh = ui.get_screen_size()   
        self.uiStyle = ui.get_ui_style()
        
        self.buttonsList = []
        self.buttonWidth = (sw - (2*8) - (24*4)) / 25
        self.buttonHeight = 40
        
        # ———————————————————————————————————————————————————————————————————
        # MAIN VIEW 
    
        self.width, self.height = sw, 50
        self.alpha = 0.98
        
        # ———————————————————————————————————————————————————————————————————
        # SCROLL VIEW
        
        sv = ui.ScrollView(name='scrollview')
        sv.width, sv.height = (sw, 50)
        sv.content_size = (2*sw, 50)
        sv.bounces = False
        sv.shows_horizontal_scroll_indicator = False
        sv.paging_enabled = True
        sv.x, sv.y = (0, 0)
        colorDict = {'light':'#D6D8DD', 'dark':'#343639'}
        sv.background_color = colorDict[self.uiStyle]
        
        self.add_subview(sv)
        
        # ———————————————————————————————————————————————————————————————————
        # BUTTONS IN SCROLL VIEW
        # ———————————————————————————————————————————————————————————————————

        for pad_elem in self.pad:
            if not 'style' in pad_elem: bStyle = 'light'
            else: bStyle = pad_elem['style']
            if 'title' in pad_elem:
                b = self.add_text_button(name=pad_elem['key'], title=pad_elem['title'], style=bStyle)
            elif 'symbol' in pad_elem:
                b = self.add_symbol_button(name=pad_elem['key'], symbol_name=pad_elem['symbol'], style=bStyle)
            self.add_scrollview_button(b)
        
    # ===================================================================
         
    def add_scrollview_button(self, b):
        b.y = 10
        if self.buttonsList == []: b.x = 8 # 1er bouton
        else:
            lastButton = self.buttonsList[-1]
            b.x = lastButton.x + lastButton.width + 4 # intervalle 4 px
            if len(self.buttonsList) == 25: b.x += 12 # 2e page
        b.action = key_pressed
        retain_global(b)
        self['scrollview'].add_subview(b)
        self.buttonsList.append(b)
            
    # ———————————————————————————————————————————————————————————————————
    
    def add_text_button(self, name='', title='', width=40, style='light'):
        b = self.add_button(name, style)
        b.title = title
        b.font = ('<system>', 18)
        if width == None: b.width = ui.measure_string(b.title,font=b.font)[0] + 28
        else: b.width = self.buttonWidth        
        return b
        
    # ———————————————————————————————————————————————————————————————————
    
    def add_symbol_button(self, name='', symbol_name='', style='light'):
        b = self.add_button(name, style)
        symbol_image = SymbolImage(symbol_name, point_size=11, weight=LIGHT, scale=SMALL)
        b.image = symbol_image  
        b.width = self.buttonWidth  
        return b
        
    # ———————————————————————————————————————————————————————————————————
    
    def add_button(self, name='', backgroundStyle='light'):
        
        b = ui.Button(name=name)
        b.corner_radius = 8
        
        colorsDict = {  'light' :({'light':'#FFFFFF', 'dark':'#B4B9C1'}, 'black'), 
                        'dark'  :({'light':'#717274', 'dark':'#4D4F50'}, 'white') }
        b.background_color = colorsDict[self.uiStyle][0][backgroundStyle]
        b.tint_color = colorsDict[self.uiStyle][1]
        
        b.alpha = self.alpha
        
        b.font = ('<system>', 18)
        b.height = self.buttonHeight        
        return b
                
# ===================================================================

@on_main_thread
def AddButtonsToPythonistaKeyboard(pad=None):
    
    def numeric_keys(): 
        list = []
        for i in range(1, 10):
            list.append({'key':str(i), 'title':str(i)})
        list.append({'key':'0', 'title':'0'})
        return list
        
    if not pad:     
        pad = [
                {'key':'tab', 'symbol':'arrow.right.to.line.alt'},              
            
                {'key':'undo', 'symbol':'arrow.uturn.left', 'style':'dark'},
                {'key':'redo','symbol':'arrow.uturn.right', 'style':'dark'},
                
                {'key':'paste', 'symbol':'doc.on.clipboard'},
            
                {'key':'#', 'title':'#'},
                {'key':'_', 'title':'_'},
            
                {'key':"'", 'title':"'"},
                {'key':'"', 'title':'"'},
                {'key':"'''", 'title':"'''"},
            
                {'key':'(', 'title':'('},
                {'key':')', 'title':')'},           
                {'key':'[', 'title':'['},
                {'key':']', 'title':']'},
                {'key':'{', 'title':'{'},
                {'key':'}', 'title':'}'},
            
                {'key':'+', 'title':'+'},
                {'key':'-', 'title':'-'},
                {'key':'*', 'title':'*'},
                {'key':'/', 'title':'/'},
                {'key':"\\", 'title':"\\"},
            
                {'key':'<', 'title':'<'},
                {'key':'>', 'title':'>'},
                {'key':'=', 'title':'='},
                {'key':':', 'title':':'},
            
                {'key':'del_right', 'symbol':'delete.right', 'style':'dark'},
            
                {'key':'find', 'symbol':'magnifyingglass', 'style':'dark'}
                ]
                
        pad += numeric_keys() 
        
        pad += [
                {'key':'+', 'title':'+'},
                {'key':'-', 'title':'-'},
                {'key':'*', 'title':'*'},
                {'key':'/', 'title':'/'},
                {'key':'<', 'title':'<'},
                {'key':'>', 'title':'>'},
                {'key':'=', 'title':'='},
            
                {'key':'line-', 'title':'---'},
                {'key':'line=', 'title':'==='},
                {'key':'line#', 'title':'###'}
                ]   
        
    ev = editor._get_editor_tab().editorView()
    tv = ev.textView()
    
    v = SpecialKeyRow(pad)                        
    vo = ObjCInstance(v)  

    retain_global(v)
    
    tv.setInputAccessoryView_(vo)   # attach accessory to textview
    tv.find = ''
    
# ===================================================================
    
if __name__ == '__main__':
    AddButtonsToPythonistaKeyboard() ```

@cvp Thank’s a lot Magic cvp👏👏👏 🙏

@cvp Thanks a lot for your work. But my goal is to get a reduced row of keys as I think that the original one is to large for the small screen of my iPad mini 4. I regret that it’s not possible to assign the fonction to a normal ui button.

@cvp Please, how do you insert directly your pictures in comments ?

My new special key row !

The only solution I've found is to make my own special key row with the help of the cvp example ;-). It's quite easy for normal keys, but I don't find solution to implement the undo/redo key? Perhaps with objC ?