Sometime ago I had an idea for a similar interface without the dragging feature. Basically, just a tree visualisation. I usually discuss a tangent topic in the same conversation, but I don't want to confuse the AI afterwards, so I edit a previous message when the tangent started. However, OpenAI would discard that tangent tree, instead it would be nice to have a tree of the tangent topics explored, without necessarily having to sort them manually, just visualising the tree.