Andreas - thanks!
I didn't think of that - it would not be inconvenient if I could do something like that.
However, I'm not sure I understand how that would work, perhaps I've misunderstood. If I export processes (either just the new ones or the whole of e.g. the unit processes database) as JSON-LD format, I think the UUID is maintained (this seems sensible). When I reimport that JSON-LD, none of those three options (never update data that exists, update with newer version, overwrite all) would end up with the imported processes having new UUIDs and both ending up in combined database.
Sorry, if I misunderstand. Again, really appreciate your comments and, of course, making this available.