The shortcut for undo (ctrl-z or command-z) is duplicated across these two files:
src/chrome/browser/ui/webui/md_bookmarks/md_bookmarks_ui.cc
src/chrome/browser/resources/md_bookmarks/command_manager.js

The first is used to generate a text description of the shortcut for accessibility technology, the second handles the keyboard events.

We should consider moving the shortcut definitions out of Javascript and entirely into C++, with C++ then passing them to Javascript for binding and handling.