Solved by JustFlight support. They saw this post but didn't put the solution here.
Solution: Select 'Chill & relax', 'Social', 'Hobbies' or 'Exercise', choose anything you want. It will show where on the printsceen is now 'Meditation'. Pick that up and drag it to one of the slots. If all slots are filled you will get a 'Continue' button above 'Slot 6'.