Google AI studio at least has this. I found at least that implementation quite confusing though, which may be a reason it's not implemented in more "consumer oriented" tools.
I've been kicking around making this for a while. BetterChatGPT at least has some good ergonomics around deleting history. But I agree that branching is the next step.
You can edit responses, sure, but then a bunch of other context is lost.
My flow is basically:
1. plan
2. build
3. branch (into some feature/esoteric dependency issue)
4. goto #2
Prompt pruning/branching should be a first-class tool for any LLM usage.