How do I know which rooms have I added?

While in Quick Add, tap on the room bar to select other rooms. The rooms at the top are the rooms that you have already added. You can select any of those rooms to adjust the quantity or items in the template. You can recognize which rooms are new by looking at its name, + Bedroom is a new room. If you select it, you will be adding a new room. The difference is that new rooms have the + icon on the left side of the name, while added rooms do not have the icon.