In that page you can edit any existing series ( only if you have any) by clicking on that series or you can make a New Series by clicking on the Create a New Series in the green box. Name your Quiz series as you like and add Quizzes of your choice.
Otherwise if you want a series with Quizzes made by different Quizmakers then unfortunately you can't do that. Like in this Empire Series, We requested Stewart to add my Quizzes in that Series made by IAB. You can contact Stewart by joining the Discord Server and may appeal to him
I was really desperate for features last year but after that I got over it and since May, I'm getting features over features (人*´∀｀)｡*ﾟ+