Ah! That’s good to know!
The default track height inside the Join GUI does not show the necessary controls to enable input selection until you increase the vertical slider at the bottom right. I did not realise this until too late, so we will try this at the next opportunity.
In the meantime I have been experimenting with Reaper but drag-and-drop from Reaper into Join does not seem to work either, however I was able to play back from Reaper and record into Join in real time, so we should hopefully be able to get this to work in Logic as well, although rendering from Logic/Reaper with subseqent drag-and-drop from Finder/Explorer is probably quicker and easier.
Thank you all for your help – I think Join has great potential, because it solves a problem I had using VST Connect working in real time with a musician in a different time zone. With Join, we can each work during our normal waking hours 