Tweaking previous AI messages

Is there a reason I can only edit the most recent message? Whenever I notice the kin repeating a thing over and over, it's typically been 5-10 messages already and I want to nuke the whole chain so the AI forgets it immediately, but I can't.

Actually, the perfect remedy for this would be a "delete repetition" tool that allows you to select a fragment from the last message and bulk delete it from the last X messages. But that's probably too much to ask.