Not possible. Those settings are for Quantum and nothing else, though if they survive a reinstall of another version they do.

What your asking is a Oxymoron

NSK24 said

I want to know how to remove Quantum but keep Firefox on Win10 without uninstalling and exporting bookmarks and settings I have. Thanks!

"Quantum" is just a fancy name they gave to Firefox when the improved version 57 was first released - see :

https://blog.mozilla.org/blog/2017/11/14/introducing-firefox-quantum/

"Quantum" = Firefox.

If you'd remove Quantum, you'd be removing Firefox, and that's not what you want to do ......