Does anyone have an idea of how to do it or even if it’s possible? Because as I am paranoid I would like to close my Mozilla account.
BONUS: How to prevent the installation of new extensions from opening welcome pages because it’s very annoying thank you.
You can just write an HTML/markdown page with your bookmarks and host it on some web server (your own or eg github). Works on any browser, from anywhere, no syncing required. You can use git or whatever. You can share it with others, organize it in any way that makes sense you to, etc.