In Eclipse IDE, the Undo and Redo actions are disabled (greyed out in menu and toolbar, shortcuts ctrl-z, shift-ctrl-z don’t work). My Eclipse version is 2023-09 (4.29.0).

The actions stopped working suddenly. If there was a specific trigger for that, I didn’t notice… Restarting did not work (as suggested here)

This is basically an update of this question, which is so old, that it may seem out of date. It is not, though.