Might this query have been overlooked or have I inadvertantly posted a long answered question?
Truly would be a benefit if possible for my 30+ operators.
101 views and no posts; my best guess is that there is no answer to your question. Too bad. I could use that functionality as well. Perhaps you could submit an enhancement request.
I don't have a solid answer - rather some observations that suggest it may not be tied to the session.
One of the engineers in our small office splits the feature tree often. Me, not so much. But I do notice on various files that he saved into the vault last, the tree will still be split when I checkout from the vault and open. So the split state does seem to travel with the file. However, I have no idea if it is consistent and more importantly, what drives it.
The split FeatureTree is a document specific setting so there's no global way to make this set. You might be able to write a simple macro and make it a button to quickly make the split.
I would suggest you open your Part Template, set the split and then save it. That way, all new parts will have the split already set. At least moving forward you'll have what you want.