Very good! But Odoo will only let you delete a Manufacturing Order if the state is "cancel" so you add the following:

rec.copy()

record['state'] = "cancel" <=== Add this

rec.unlink()

Thank you, Jake and Chris, your both replies are very helpful.

I created the server action and it works almost fine. The thing that is not copied was the Source (the origin which refers to the sale order). I managed to copy it as well.

But my question is, why it was not copied? Could it be possible that I lose other data like this and how can I handle it?

My initial purpose to copy and delete MOs is to make it possible to change the Routing in the new MO (since it is not possible after the creation of workorders). Do you think is it a good idea or should I do it in another way?

The field origin is not copied (as per base properties). You can check which fields will be copied by looking at the model definition or field list.

It may be possible to change the model definition so that field is copied, but that's not my area of expertise!

In my opinion, it makes sense that Odoo doesn't copy the origin field (though I understand why you want it)