That's not the editor, that is GM Mode.
SO I just found out that DOS2 has only a DM mode editor and no stand alone editor
Not true.
The editor is called The Divinity Engine 2 and is a seperate download and let's you do just about anything. Create stand alone adventures or make maps/scenes for GM Mode.
After launch, Realms Beyond will also get a DM Mode.
I have to say I am very curious about that as DM Mode is what brought me to DOS2 to begin with and is a must have for me to even buy BG3.