I thought the main point of this issue was to define standard functions,
methods, classes (or something in that sense), in order to make the
creation of tk dialogs uniform across IDLE.

Right now it seems reasonable to keep the parent hidden, but I think it
may not help much for maintaining. I really consider a good idea to
define explicitly who is the parent of a dialog, it wasn't an attempt to
refer to the phrase you cited.

I trust you it reduces the size on that file, I really didn't count how
many lines were removed and how many were added, but these dialogs can
be used anywhere around IDLE so I don't see why keeping them inside
EditorWindow is a good idea. It would reduce even more (some few lines)
EditorWindow's size doing so, and it would make more sense as I see.