The idea here would be a quick action to make inventory qty at least equal to qty in deck. I don't keep track of my entire inventory but it's helpful to know what I have of at least the rares that I've used to build other decks. This could also provide a solution to https://deckbox.org/forum/viewtopic.php?id=28865 - just do a mass import from a list from elsewhere, then select all and hit this new action and your inventory is updated automatically.

This is similar to the "Add to Deck & Inventory" feature but en masse as opposed to one at a time and something that could be done after the fact, not necessarily as it was added to the deck.