Lines that match the room
More than one line per location, and a line per chair, bay, counter or person. Somebody waiting for one particular member of staff waits behind that person's line, not everybody's.
A location can run several lines at once, and each line can have its own chairs, bays, counters or windows. Somebody who asks for a particular person waits behind that person only — so a busy stylist does not hold up the whole shop, and the customer who takes anyone gets seen sooner.