You don't need a level to book a court. You do need one to create or join any padel or tennis match, and to join any padel or tennis activity. The app asks you to set it the first time you need it.
You need a level for
Creating or joining a padel or tennis Public Match or Private Match, even when the level range is only Suggested.
Joining a padel or tennis activity, even one with no level requirement.
You don't need a level for
A Court Booking.
Sports without Nettla levels, such as pickleball, badminton and squash. These sports have court bookings only, not matches.
Required or Suggested
Matches and activities can have a level range:
Required: only players inside the range can join.
Suggested: the range is a guide, and players outside it can still join.
Which sports have levels
Padel: your level changes automatically from your match results.
Tennis: you set your level once. It doesn't change from results; only your club can change it.
Good to know
To set your level, see "How do I set my level for the first time?".
Some clubs' own apps use their own level scale, so you may need to set a level there separately.