You can sync two Things instances between two Macs easily by copying ~/Library/Application Support/Cultured Code/. But this works if only the donor instance has diverging changes. What if both instances have unique new items?
You can sync Things iPhone to multiple Things.app instances. My problem was that items move from a Mac to the iPhone, but not from the iPhone to the other Mac. And this is the solution for merging Things from one Mac to the other:
- Bring up Things on Mac A, sync iPhone, shut down Things.
- Bring up Things on Mac B, sync iPhone, shut down Things. Now iPhone has items from both Macs, but Mac B doesn't.
- On Mac B, remove/backup ~/Library/Application Support/Cultured Code/Things/Database.xml
- Pair and sync iPhone to Mac B again.