Changing the Input Map in Project Settings (adding/removing/renaming actions, reordering, or changing action events) causes the action list Tree to be cleared/repopulated. Updated ActionMapEditor::update_action_list to store which actions were collapsed before clearing, so they can remain collapsed after modifications.
The previous default value of `3` made gizmos too large and cluttered the viewport, especially on smaller screens. A value of `2` seems perfectly usable and provides a more comfortable default.
