Removing Ctrl-Z undo entirely would be better than the current state. The current state of undoing rules doesn't seem useful to anyone; I rarely find myself needing to undo rules, and if one needs to, they can just delete the rule.

It would be ideal if the text fields stored each input after the field is not selected for later retrieval. Then there would be two possible ways of implementing the undo history: it could be local to each text field, so it only applies to the text field when it's selected, or it could be local to the current rule, so it could undo text inputs across different fields and even the option checkboxes.