Blender's Assign Shortcut just adds a key. Hotkey Tool Manager -Warns you before a key overwrites an existing shortcut. -Lets you choose where it works (3D Viewport, the editor you're in, or everywhere). -Shows every shortcut something already has. -Undoes all its changes in one click without touching your other keymap edits.

- The Shift + Right Click window and the right-click menu entry disappear immediately. - Shortcuts you already made KEEP WORKING, because they are normal Blender shortcuts. To remove them, turn the add-on back on and click "Reset All Hotkeys" first. (The add-on's list of changes is kept in a tiny file, so turning it off and on doesn't lose it.) - Alternative without the add-on: Edit > Preferences > Keymap and click "Restore" next to the changed keymap groups. Note that this also removes any shortcut changes you made yourself.

- No, not after installing or assigning shortcuts.