Two new additions for premium accounts today, which should greatly improve the Inventory-Deck interactions, and deck-collection interactions.
The quickadd inputs in decks now have a little checkbox called "From Inventory". Clicking it will cause the autocompleter for the quickadd to only search your inventory cards. When selected for addition the cards will be added to the deck automatically with their details set (edition, foil, etc).
Secondly, in the add widget in decks (the one that opens when clicking "Add Card") there is a new tab called "Add to Deck & Inventory", which allows adding cards simultaneously to the current deck and the inventory. After selecting the card name, the count, details and deck section can be also set for the card to be added.
Feedback & bugreports are much appreciated, as usual. Have a nice weekend!