does it work with thunderbird started in safe mode? https://support.mozilla.org/en-US/kb/safe-mode-thunderbird

It does work in safe mode. So I guess your going to say that an extension is the problem? When I upgraded and disabled and extensions not compatible. But the problem still persisted. Is there a next step?

Yes, disable addons individually or in small groups to narrow down which one is causing the problem.

Please let us know which one you find is causing the problem.

Yep I shoulda thought of these steps. I seems to be due to the quickFolders add-on. The move works as long as this add-on isn't on. I've emailed the developer. I'll see where that gets me. Thanks!

Funnily enough, QuickFolders has its own "move to…" keyboard shortcut which I've never been able to make work. ISTR this is a "premium" mode function which is enabled only when you pay the fee (as I have done.)

QuickFolders also has a graphical drag-and-drop mode where you drag selected messages to a toolbar icon and a dialog appears for you to type in the required target folder name. This is similar to the functionality of the QuickFolderMove add-on, which is also broken In TB45, though probably because the generic underlying "move to…" action is broken by QuickFolders.

Worked with the Dev and it looks like he squashed the bug. Do't know a time on final release though.

Interesting. I had an add-in called something along the lines of "ConfirmBeforeDelete" that I used in v 44 or older for reasons I don't remember now, and disabling it fixed the Move To issue. I've since removed this add-in.