Impossible to roll back a card to "missing" status in list

I'm trying to recreate a correct list of Sorcery beta actual card in my possession. So far I jsut created a list of my missings. So i decided to put a little time in recreating a full playset one using the creation tool. And then I tried to find a way to identify the 100+ card I'm actually missing. In order to do that I changed the status of all the card ine the new list to 'in my possession" in order to roll back the missing ones to "missing" but I cannot do that. Also I tried to supress my missing card indivually in the "possession" list in order to import the missing list again hopping these imported card would be marked as missing as when I'm creating the list in the first place but no. It has adding it to in my possession event thought I was in the missing product display...