In case you mess up the schema for any reason and you are no longer able to open the Gnome settings, e.g. gnome-control-center, just do the following and then logout and back in (or simply reboot):

rm .config/dconf/user

That’s it! Enjoy!

Sources:

https://www.linuxuprising.com/2019/03/how-to-reset-gnome-desktop-settings-to.html