Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding Troubleshooting Run missions from editor like in real game.

You can certainly still playtest in the editor though in game mode. If you want to do it with a specific created character you could add a testing only character to the map, set it as a player, and give it the appropriate stats/skills.