It is now possible to undo basic file operations and to redo them. Undo and Redo can be used for 'move', 'rename', 'trash', 'link' and 'create' operations. Per default, a history of the last 10 operations is stored, though the history length is configurable. Whenever an Undo/Redo is triggered, a notification with few details will be shown.
~/.config/xfce4/terminal/accels.scm looked promising but my changes were undone after a restart, so I made it read-only but it turns out commenting out the relevant lines makes no difference anyway.