It's currently not possible to see the exact structure of a conversation (thread) and therefore also difficult to navigate within it (it's currently just a flat list sorted by date).
It would be useful to have something that allows us to see where within a conversation we are, and navigate to other messages within the conversation.
One example mockup how this could look like is M31, but we'd have various problems to solve still.
The visualization would have to be always visible as we scroll down (I think), and given that branches and a linear view in the conversation view don't really match it could also be confusing (messages from various branches of the conversation are interleaved since only sorted by date).