Yes. The Workout Planner lets you build your own week from any workout in the app, as many or as few per day as you want.
On Home, scroll to More and tap Workout Planner.
Tap the pencil icon.
Tap the + on a day, pick a workout from Classes or Gymstyle, tap Schedule.
Repeat for each day you want to train.
You can do this alongside your active program too: keep the program days and add your own sessions around them.
A common use: alternate an Upper Body Build day with a lower body class the next day, for an upper and lower split.