Select a set of messages then Ctrl+S to save them as eml files. Eml files can be opened in any mail app, or imported to a subfolder of Local Folders in TB by drag and drop from File Explorer.

Thank you, but I need a little more help since I am not familiar with "Eml" or "TB." I think you are saying to select emails to transfer and then Ctrl+S. Then what? And will a copy of the emails move or will that happen and the emails will be deleted from Thunderbird page?

Select one message, then Ctrl+S to save it as a file with an .eml extension, to the directory of your choice. Try it, the message remains in TB.

Almost there. How do I "save it as a file with an .eml extension"? I'm on a steep learning curve, and you have been very helpful.

Got it!! Thanks again.