Agree with colditz. i think it's really important to distinguish between normal, curious, investigative or imitative behaviour like this microwave thing, and real naughtiness that you need to impose a consequence for.
With the microwave thing, and similar stuff, this isn't naughtiness that needs punishing; she's imitating, playing mum basically; I think toddler proofing is much the healthier way to go and will save you from feeling you have to DEAl with so much stuff. If the microwave can't be moved up out of reach, put a stairgate on the kitchen doorway so that she can't reach stuff in there. Or have a playpen that you can stick her in just for loo trips or turning the oven on...
don't feel you need to deal with every action....most times it's enough to say "oh no, we don't touch the microwave, that's hot hot hot....let's help dolly do her cooking instead" or whatever...it's distraction basically.
i think you need to try to toddler proof like mad and don't be afraid just to say 'No' and divert her attention. So much doesn't need punishing, she doesn't need 'training'....tell her what you want her to do, give her the chance to comply....
and I hate naughty steps personally, i just think they create such a lot of work in trying to keep the child there, returning them endlessly....I think if the child has been given chances to moderate behaviour and they are being totally impossible and defiant then 1 minute in another room on their own is far, far easier all round.