There is one interesting (and important) fact about Workset 1 which an earlier post hinted to: it acts like Layer '0' in Autocad.
Take two workset files A.rvt and B.rvt.
Link B.rvt into A.rvt. Draw some stuff in Workset 1 in file B, make sure Workset 1 is set to Visible by Default.
Back in file A, you should be able to see the objects from file B. All well and good.
Now switch Workset 1 in file A OFF, ie, set it to Not Visible or Closed.
Where did all your things from file B go? 🤔
Yes, Revit fans, if you switch off Workset 1 in your master file, you switch it off in ALL linked files. Also this behavior happens even if you renamed the worksets, so that super-important workset BUILDING_CORE_VERY_IMPORTANT (originally Workset 1) will suddenly and silently vanish if someone switched off the innocuous Workset 1 in the master file. Mayhem ensues...
What could possibly go wrong with a simple, easy-to-understand and totally obvious 🙄 system like that?
Why would anyone expect the contorted logic of Layer 0 to be brought into the modern, truth-centric world of BIM?
In short - friends don't let friends use Workset 1.
Ok, actually I use it all the time. I leave my default workset as Workset 1; but at the end of each day I spend 10 minutes tidying up all my work (and anyone else's work, hey I'm the BIM manager) and putting it on the correct worksets, which are something other than Workset 1.