Seasons of Drabbles

Hiya, I haven't done this event before so apologies if this is a well-known fact. However, I'm confused about how to sign up for fandoms that haven't been approved to the tagset yet. If nominations and sign-ups close at the same time, what should I do about fandoms I want to sign up for whose tags aren't approved and can't be added as a sign-up? I know there's a grace period for adding tags, but does that also go for adding requests?