I want to recast this as a doc issue.  The BINDINGS section of http://www.tcl.tk/man/tcl8.6/TkCmd/text.htm, near the bottom, has a list with 33 numbered items.  The main categories of action include selection modification, cursor movement, and text deletion.  Minor categories include insertion, transposition, undo/redo. However, the items are not neatly grouped this way.

Some of these actions are IDLE menu items and are listed in the IDLE menu doc.  Many more are documented in https://docs.python.org/3/library/idle.html#editing-and-navigation.  Some useful actions, such as ^t Tranposition Right, are omitted.

Some of this IDLE doc is wrong, at least for IDLE, at least on Windows.  For instance, at least on Windows, ^a in IDLE is Select All, not Move Beginning of Line.

For working on IDLE, it would be very helpful to have a *categorized* listing of class-bound actions that are verified to work for tkinter Text, with notes on any OS differences.  I can then check what works on IDLE and how it changes the bindings on either some or all systems.  I can and someday will do this for Windows, but I currently would need help for other OSes.

To help people avoid clashes such as Nick ran into, the tkinter doc should also have a sorted and abbreviated list of bound event sequences.  "Text comes with bindings for the following event sequences for keys: Control-a, ..., z; Control-Shift-?, ...,z, Meta-...(Unix), Command-...(Mac).  For mice, ..."  Follow with a note on what can or cannot be unbound and the need to use 'break' when overriding.

A function to produce for IDLE a similar list that includes IDLE's system-specific add-ons and a user's customizations, would be a separate but very useful issue.  Not knowing current bindings makes customization hard.  Another spinoff issue would be making actions available via the IDLE menu system.