You stop syncing in the app settings. Just turn off the checkmark in front of the databases you do not want to sync. Or turn of the sync location completly (that’s also a check mark).
By ‘empty’ do you mean select “Clean Database…” from the right-click contextual menu for each database? I wasn’t sure whether or not this might have been the method, or whether I should select the “Clean Location” contextual menu selection under the Dropbox ‘Location’, rather than the “Clean Database…” contextual menu selection for each database. Neither was I sure which method would erase the data in Dropbox (perhaps they both do).
Perhaps cleaning the ‘Location’ is to do the erasing globally, rather than cleaning selected databases on a piecemeal basis? I’m looking for the ‘global’ option, and as I say to erase the data at Dropbox.
As I said, I do have databases in the “DEVONthink To Go” iOS app (the ones that have been synced there from the macOS app). I’d like to keep the iOS app for future use, but just delete its current contents and syncing.
The Help and the DEVONthink Manual has guidance for all this.
Yes, “clean” a database deletes it from the sync location, e.g. the Dropbox server. There is no global “clean”. Do it for each database you wish to remove from the sync location.
Cleaning does not delete the database on the iPhone. Delete it there. Deleting on the iphone does not delete the copy on the macbook.