It doesn't really make much sense for the control plane switch to be in preferences. It's a setting that's tracked by the Tailscale daemon, and synchronizing that to the preferences in dconf is a tad strange. I think it would make more sense to move it out of preferences and into a separate menu option that, when clicked, opens a dialog with a field to enter a control plane URL and three buttons, one to cancel, one to use the entered URL, and one to switch back to the default.
It doesn't really make much sense for the control plane switch to be in preferences. It's a setting that's tracked by the Tailscale daemon, and synchronizing that to the preferences in dconf is a tad strange. I think it would make more sense to move it out of preferences and into a separate menu option that, when clicked, opens a dialog with a field to enter a control plane URL and three buttons, one to cancel, one to use the entered URL, and one to switch back to the default.