It looks like the bar is positioned differently in your Firefox, but I don't know why. I'm attaching mine for comparison, but yours has many more buttons. Maybe that is a factor??

Well, that's the problem.

In Firefox it is out-of-whack (my image #1), but in my OLD Brave browser version, it works fine (my image #2).

I don't know if having extra Wordpress buttons has anything to do with it, but it should just work, like in Brave.

Thanks for the reply.

Thanks for the ideas:

1. Clearing the cache and cookies did not help, unfortunately.

2. It WORKS with Brave browser, as stated in my original call for help.

3. I de-activated all of the EXTENSIONS and that did not help.

4. I don't know how to check the theme's functions.php file for errors. I looked it up on the web and seems way beyond my expertise. Since I have only had this problem since moving to Firefox (from Brave), seems it would be a Firefox issue.

5. Reinstalling core files: I don't know how to do that either, but as I stated in 4, since Brave works fine, seems to be a Firefox issue.

6. When you write "plugin" do you literally mean "plugin" or "extension"? Firefox has both. I disabled all of the "extensions;" and unfortunately, it did not help as stated above.

Thank you for the ideas.