--alternate-destination-marker not supported?

If you meant Windows Task Scheduler, some people do use it for Duplicati, but I’m not familiar with its abilities.

https://forum.duplicati.com/search?q=%22windows%20task%20scheduler%22

I think you might be asking for trouble going back to identical drives, but there might be a different check that would avoid disaster. Duplicati by default has a good look at the destination file list to see if it’s as expected…

Please test it to see what error it gives, but don’t try to use –no-backend-verification to turn off the safety net which is probably what’s being referred to here in the How to test which database belongs to which job? topic.