Does shift+m work for you? It does here but I can't remember whether or not this is courtesy of an addon. I know of two addons which offer an enhanced move, QuickFolders and quick folder move. Both allow you to search for a folder by typing and it autocompletes, much like filling in email addressees from the keyboard.

One you have a shift+m capability you could probably use the custom buttons addon to make your own toolbar button. You'll probably also need to look at the keyconfig addon to discover the code and command to use to fire shift+m from your new button.

I use "move to" a lot myself, but have been perfectly happy with shift+m; I am going to have to type the destination folder, so it's not optimal to use a mouse to trigger the process. Shift and m, then two or three letters and you will have found the required folder in an arbitrarily large and complex folder tree with about five key presses.

Thanks for your option. It does work, although I have an addon that does the same thing. The problem is that I have multiple subfolders, which is where most of my email files are held. Message --> move to opens up layers of subfolders (from each primary folder) so I can drag emails in the right one. Also, even if 'shift m' did open up the subfolders, and since I am using the mouse a lot, it is awkward to do it with the left hand. I expect that I will have to go the route of making a custom button. Can you help with that?

anything here https://codefisher.org/toolbar_button/toolbar_button_maker/en-US/messenger/

From the same folk that bring us https://addons.mozilla.org/en-US/thunderbird/addon/toolbar-buttons/?src=ss

Neither of these has an icon for the 'move to' function in Thunderbird.

What about the File icon that you can drag to the toolbar from the Customize... window?

Hmmm.. not sure I can how that would work. However, I just realized that I can right-click a message and do a 'move to' from there.