That's what I originally did.

I don't want to transfer Firefox data to ANOTHER computer. I want to transfer (import) the login file (saved passwords) from one profile to another profile on the SAME computer, or even import other data like saved themes and other saved preferences. But I don't want the accumulated windows and tabs of the source profile.

If I can just manually move the logins.json file from one profile folder(source) to another profile folder (destination) that might solve the problem. But many years ago I tried that and essentially broke Firefox and had to use a backup Firefox folder to quickly restore the browsers function.

Again, I just want to copy (import) the logins from one profile to a newer profile on the same computer. Thanks

According to this article:

Recovering important data from an old profile https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile#w_create-a-new-firefox-profile

"Passwords Your passwords are stored in two different files, both of which are required: • key4.db This file stores your key database for your passwords. To transfer saved passwords, you must copy this file along with the following file. • logins.json Encrypted information about your saved usernames and passwords. For more information see Password Manager - Remember, delete and edit logins and passwords in Firefox."

Hopefully copying these two files from old to new profile folder is all that is needed. I have never tried this myself!