Sometimes in a discussion with an AI assistant I want to explore a tangent and then come back to the main topic. I envision scrolling back to the the beginning of the tangent and then click 'branch' on the last relevant response to start a new branch.
This would also be useful when a discussion didn't produce a useful result, allowing me to go back to the last relevant response and branch from there.
I just envision a discussion as a branching tree instead of just a single linear chain of prompts and responses.