When you have something selected on the tree view, at the bottom of the screen right above the search bar, there is a bar where the branches leading to the thing are listed in order from most general on the left to the thing on the right. If something is nested under multiple things and thus belongs to multiple branches, only the branch corresponding to your selection in the tree is shown. If you want to see what other branches the thing is on, you have to go to the record.
A nice way to show what other branches it's on would be for those all to show up at the bottom. The one you've selected could be on the bottom, or the top, or whatever, and the rest would also show up. If something shows up in like 40 branches I guess that would be a lot of stuff and so maybe that area might some day need a scroll wheel, but I suspect most things only show up in a few branches at most, so you'd only have a few things stacked on top of each other.
Have you ever tried clicking the Next/Previous buttons when in the Tree tab? It takes you to the next instance of the selected record. So you don't actually have to leave the Tree tab for that.
However, I agree that a better solution is needed to see the other branches at a glance. I looked and quickly found a record in my Tree with 53 instances. So I don't think showing all the paths stacked together will work. I think a better solution would be a view that shows a tree view with only the branches that lead to the selected record. That could be in a popup window, or (I think this is my preferred solution) the bottom pane, which usually only shows the record description, could have tabs. The second tab would be a tree view only showing branches for the selected record. Or it could be a reverse ancestry view: the selected record would be the root, the next level would be the immediate parents, etc. Maybe forward/reverse ancestry should be toggleable. Let me know your thoughts.
I don't really use the Next/Previous buttons, so no, I hadn't noticed that. That does help a bit, but if I have to click a button I might as well just open the record, which lets me see everything with a double click, rather than having to hit Next as many times as there are other branches.
Another tab in the bottom pane would work well. It's a shame to make Hypernomicon more cluttered up with tabs, but this might be a reasonable tradeoff.
Another possibility to avoid more tabs is that the main Tree pane could switch to a dual view with the main tree on the left and the tree only showing the selected record branches would be on the right (only the main tree would show by default).
Any thoughts on reversing the ancestry direction so that the selected record is the root of the tree?
I'm not sure about the split view. I'd probably have to see it and use it to know if it's useful enough to pay the price of splitting the tree view in half and thus seeing less (and having a more cluttered view).
A toggle for the reverse might be nice but again since I'd have to click on it, I might as well just open up the record.
I think ultimately since some things might be parts of so many branches, there isn't a super good solution to showing this in the tree. It's very visible and legible in the record itself, so maybe that's good enough.