drffc wrote:
Safe Mode did not change the behavior.
Do you have another suggestion? :-((
Safeboot was one out of 4 suggestions above(?)—you make no mention of the alternatives
What did Fire fox say?
Did you try their help page— https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings
Can you verify FF is in your Applications folder? Remove the FF icon from the Dock and drag a new one from the Application folder back down to the Dock.
I have never seen this issue before, open windows populating the right side of the Dock.
Why so many open windows— hardly seems practical.
I would close out all those windows—I would disable all FF add-ons, quit FF. Down load a fresh copy.
Uninstall all third party apps that are Cleaners/Optimizers/Anti-Virus/VPN
You can trouble shoot further—
—Test issue in another user (or guest user) account https://support.apple.com/guide/mac-help/set-up-other-users-on-your-mac-mtusr001/mac
This will tell you if it a universal issue or isolated to your user/admin account.
Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus all know to cause issues.
If no resolve try a different browser, if you are not willing to explore the issue with FF Support and issue w/ the current version and your Mojave 10.14.6.
Revert back to an earlier version of FF prior to the issue as already mentioned above(?) if you want to side step the issue as is.