Manage spots available in advance for specific days of week

I would like to be able to reduce the number of spots available for a specific day of the week (for example for a service with 4 spots available all week long, on Monday it would be only 3 spots, throughout the year)… for now if a customer booked in direct a spot every monday throughout the year, I can only make this spot unaivable by creating one by one bookings every week along the year to reserve one spot...

Best would be to have an available spots calendar in the back-office where we can easily click on the day and set the number of spots available, this would make it really smooth and easy to manage when you have customers who book in direct and not online for a recurring service (in my case co-working space)