We travel with a group of 9 often.
There are some restaurants that book larger tables. For the ones that don't (which is the majority), I just book a table of 4 under my account, and a table of 5 under my husband's account, for reservations 5 to 10 minutes apart. We check in a little early and explain that our reservations are together, and ask if they can seat us next to each other if possible. Sometimes they offer us the option of waiting longer for tables together. Sometimes we don't take them up on it, and settle for two tables further apart but a shorter wait to be seated.
The nice thing about the newer dining reservation system online and in the app is that you can pretty easily tell right away if the restaurant will book a table for 10 or not. Pick a restaurant, put in 10 as your table size, and if the availability calendar shows zero bookings available, that's a pretty solid indicator that they don't book that size.
Play around with groupings: 5 and 5, 4 and 6, 4 - 4 - 2, to see how the availability changes for something you really want.
One of our favorite restaurants for large group seating is Morimoto Asia at Disney Springs. Bonus: they take reservations over the phone 90 days out, so it's always an easy reservation to secure.
Just a note: I have not had success linking our tables via the phone in the past. I was always told to just ask the restaurant upon checkin the day of our dining reservation. YMMV.