Cannot get iCloud Sync working

Cannot get the new iCloud preset-based syncing working. Running 2 Macbook Air M4s on Tahoe 26.6 each with the latest alpha of BTT (6.594).

I have two presets, 'work' on one MBA and 'home' on the other. Ultimately I would like to merge them and run just one preset across both machines. Each Mac is syncing its own preset to iCloud successfully ('up to date in iCloud' in Preset Sync Status) but I can't get the other preset to show up on the other machine.

Sometimes I get this error:
'Refusing sync import for preset D24C2665-7360-4C78-B8CB-506775291027 because incoming trigger UUIDs match a different local preset (Work / 075AA7B9-166D-466A-9A68-DA2644B96210).'

Legacy synchronization options (thanks Andreas for tidying the UI btw!) are turned off. iCloud sync for BTT is turned on in Mac System Preferences.

I attach a screenshot of the sync configuration on one of my Macs. But please let me know if there's anything else I can share.