While reviewing, I decided to draw a widget tree. I believe it would have been easier if packs and grids were grouped.
I want to continue with 'IDLE: modernize help-about' and ditto for textview. The help_about issue can begin with ttk conversion: change imports and remove an invalid option or two. The textview issue can begin with the still missing docstrings. I want to refactor both the way I discussed in the roadmap issue: make separate Toplevel and Frame subclasses. The Toplevel subclass instance creates a Frame subclass instance which becomes an attribute of the toplevel. Help.py already has this structure.