I have version 1.6.6 (86) and am using Dropbox to sync my iMac app with my iPad. It appears to be working.
But I cannot find a tododatabase file anywhere, despite multiple Spotlight searches. As a result, I have zero confidence that I am creating a retrievable file.
As a result, I created a Things to Do Folder in Dropbox and have been able to save and backup files.
What's going on? Is the database a hidden file?