Sync Local Moss Workspace
Use this if your current Moss workspace is local today and you want Dropbox, iCloud Drive, or OneDrive to sync it.
Put your Moss workspace in your cloud service
Make sure your Moss Workspace is tracked by the sync service you use. If you have not changed the default Workspace Location, your Moss workspace is at ~/Moss.
Keep that folder downloaded on this Mac
Make sure the synced Moss folder stays downloaded on this Mac.
In Dropbox, right-click the folder and choose Make available offline.
In iCloud Drive, Control-click the folder and choose Keep Downloaded.
In OneDrive, right-click the folder and choose Always keep on this device.
Change your Moss Workspace Location
In Moss, open Settings. Change Workspace Location to that synced Moss folder.
Choose the main Moss folder, not the Notes folder inside it. Moss will ask you to restart.
Restart Moss
After restart, Moss uses that synced folder as its workspace.
When you edit notes in Moss, Moss updates files in that folder, and your cloud service syncs those changes.