You will able to abort the mission if you can't exit a mission during the mission and you can also abort the mission in DYOM after you test it you press CTRL + A to abort the mission instead of dying.

If dyom don't have abort the mission option while testing for some bugs, missing something or crash or even actor balls, you can abort a mission when you get stuck instead going to new game, you will always continue on your work.

Press CTRL + A to abort the mission that you don't want to do