I don't quite get this umbrella thing.
So let's say you have John, Susan, Timmy, and Daisy on the resort reservation. On the same MDE, you have set up phantoms Mickey, Minnie, Buzz, and Belle. (There is no limit to the number of people you can add to your MDE. Though of course there is a limit to the number of people you can add to your reservation.)
Now you want one set of three FP for each foursome (representing one real foursome, of course - enjoying the luxury of six prebooked FP per day for each guest). But you can only prebook for the phantoms at 60 days out if you include at least one person from John & Co's group (since they're on the reservation).
Click to select new FP and toggle Mickey, Minnie, Buzz, and Belle -- and also John. (Without John or one of the other resort guests, Mickey & Co. can only get FP at 30 days, not 60.) So you prebook FP for that group of five people. Once that's done, go back in and cancel John's FP. The FP for Mickey and his family won't be affected. Now prebook FP for John, Susan, Timmy, and Daisy. You will end up with two sets of FP (six per person) booked in advance for those four people. It'sgood to know-- once the three FP are booked for the non-resort guest phantoms, youcan modifythose three FP without a resort guest needing to be toggled as part of the FP group.