I have a GSX folder in Addon Manager/Couatl/
That's not what I asked. You said you had no add-on.xml in the P3D v4 add-on folder, which is normal, assuming that with "the P3D v4 add-on folder", you are referring to the place where the add-on.xml are normally located, which is under
Documents\Prepar3d v4 addons.
As I've said, you are NOT supposed to have a separate add-on.xml folder for GSX, because it's activated by the add-on.xml folder located in the Addon Manager folder UNDER Documents\Prepar3d v4 addons.
So, do you have it or not ?