Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding General Cannot find The Divinity Engine 2

You shouldn't need to reinstall the game. Although maybe by restarting Steam, it detected that an update became available and it's installing that now? (which in turn is necessary for the editor)

I Believe the Divine Ascension version includes extras on top of the regular game (like the sound track). The base game (and editor) should be identical to the regular version though.