so i started d2 again after like 7 years (i even can not sign in my 2009 d2jsp account :( ) and this time i play sp. i have almost perfect layouts for all mf run places (6 superchest linear LK, 3 teleport andy etc.. ) i'm really afraid to hit the nightmare button when i'm about login and ruin all the joy. is there any way to reach this layout if i do something stupid ?

Hit control alt delete, and close program That way. That way it dont save it.
Ive tested it and it works

it's funny that it happened just before i read your post. somehow i did exactly what you said and can confirm it really works. thank you sir ;)

Press h