I'm using KeePass for a very long time now and was never relying on the history or synchronisation feature and I have no plans to change this. For the history we can disable it in the Database Settings and also remove all existing entries in the Database Maintenance if we delete all history entries older than 0 days.
For the synchronisation data (I assume this is all what "Deleted objects information" in the Database Maintenance references to - correct me if I'm wrong) once I delete a database entry I have also to remove those objects in the Database Maintenance - there is no option in the Database Settings to prevent keeping them (e.g. deleting a database entry would also immediately delete those objects - visiting the Database Maintenance would not be needed anymore).
Thus I'm creating this feature request as it would add quite some convenience for this case as it effectively removes 1 additional step every time I'm altering and saving a database if I want to always keep it the smallest size.
There is no sync data in KeePass. A sync is performed by comparing the entries and using the deleted object info to remove items. Removing the deleted object info prevents sync working correctly.
Personally I think you are wasting your time clearing history and deleting items. The database is never large unless you store lots of attachments, so you are only making work for yourself.
cheers, Paul