Select Side Door Collection when Saving

Currently when I add products from a mood board to my SideDoor Collection, it requires me to create a new collection. If I already have a collection for that client, I would love to have the option of adding to an existing collection so I only have to present one collection to the client. Right now, each time I create a new moodboard of options, I have to create a new collection. I am presenting a few options to my client, and we may keep some items from one collection and some from another moodboard in another collection.