Hi Pablo
It is not clear which kind of movement you want to post for the scrap. Is it a goods issue for the components or a receipt of waste material?
Please read carefully my previous reply again. As I mentioned before, there is only one field for changing the movement type for goods issue and it is valid for all the goods issues, comming from scrap of from a valid goods receipt. If you need to use an specific goods movement to post the goods issue from the scrap, you can try using the recommended BAdI.
Otherwise, if you are posting a receipt of waste material, you should use the by-product, as already refered.
BR
Caetano