Actually, my experience is still at the beginner level - I switched only weeks ago. If you have 3 branches, you can create a new node that is the merge of all

Actually, my experience is still at the beginner level - I switched only weeks ago. If you have 3 branches, you can create a new node that is the merge of all 3. But your question is will it keep up with the changes. If all 3 branches are local to your machine, and have not been shared, and you edit a prior commit, then all descendants are rebased and thus that merged node will get the changes - no new merges needed. I think your real question, though, is if one of the branches gets a new child node, can we have the merged node dynamically merge from the new child, rather than from its parent? I honestly don't know - but I actually do have a need for this! jj has bookmarks, and you can create a merge using bookmarks, but whether the new node will autoupdate if the bookmark moves - something I'd need to experiment with. Finally, when you have shared/pushed your code, jj will treat shared nodes as immutable, so some fancy jj stuff becomes disallowed.