I don't know of any automatic tool that would do this. The action of adding a star won't trigger any other action. You can set up a filter to act on messages with stars, and have it move them to a designated folder, but the filters only run automatically on messages as they arrive in the Inbox. You'd have to run the filter manually after setting the stars by hand. It's more common to use a filter to automatically apply stars. Filters operate on key words found (typically) in the sender, subject or message body and can move messages automatically, thereby totally avoiding the need to filter them "by hand" and mark them manually. You could just select all the relevant messages (ctrl click) then move them ''en masse'' to the required folder. No need for stars. Or you could manually star your messages, then use the QuickFilter bar to display only starred messages, allowing you to select them all (ctrl+a) and then move them (right-click|move to...) to the required folder. But I think some time spent learning how to use filters would be a good investment, and a better use of your time than having to manually mark messages in perpetuity.