In Hand and Foot, after completing a melded book, can you add a wild card to it? For example, once you have completed a book, but have a wild card left in your hand, can you add the wild card to a previously completed book, in order to go into your Foot or to go out?
According to Pagat.com:
A meld cannot contain more than seven cards, and a partnership is not allowed to have two incomplete melds of the same rank, but if you complete a pile, you can then start another meld of the same rank.
So not only can you not add a wild card, you cannot add any card. You'll need to attach it to another meld in progress, or make a new one.