Toggling user.css with a shortcut

I know you can temporarily set options by starting Darktable from the command line, like so:

darktable --conf themes/usercss=FALSE;

However, I’m wondering if this can be toggled with a shortcut after you’ve already started Darktable. Is it possible?

No I don’t think it is. You’d have to go into settings and tick the box (though you can create a shortcut to open settings).