ui.Views can still be presented in "sidebar" mode in Pythonista 2.0 (sort of)
Perhaps someone else thought of this already, but this just occurred to me.
ui.View().present("sidebar")no longer works in 2.0. However it is now possible to put the console slide-over panel into a similar "sidebar" mode. And you can present a view there using "panel" mode. So you can present a "panel" view, dock the panel, and now you have a "sidebar" view again. (As a bonus, it's now 320pt wide too, instead of the old 200pt.)
One nice thing about the sidebar was that it could be narrower than 200 pt, so a 30 or 40 pix wide sidebar worked well for creating custom auxilary shortcut bars in the editor without sacrificing too much width. But so much more can now be done in objc, I am not complaining.