Right now you can only diverge branches from a node. If you want two branches to converge on one you have to manually use a line connector to connect the second branch to the one you are converging on.
This second branch made from a line connector also can’t be colour matched to branches, and doesn’t respond to the auto-alignment button (it means the line may overlap text and doesn’t respond in the same way as normal branches that generate off nodes.
This sort of functionality would be great when you find overlap in ideas further into the conceptualization process. Otherwise it becomes a spaghetti mess.
I imagine it’s not easy to pull off, but very worthwhile once done!