Missing some panels in gnome-control-center? No “Online Accounts”? No “Sound”?

Apparently, panels are defined through .desktop files in /usr/share/applications (!), and they mostly have the setting of OnlyShowIn=GNOME; or OnlyShowIn=GNOME;Unity;.

To trigger them appearing in, say, i3, xfce or similar, you need to pretend you’re actually running GNOME by exporting the XDG_CURRENT_DESKTOP variable with the value of GNOME.

#!/bin/sh
XDG_CURRENT_DESKTOP=GNOME gnome-control-center