Have a go. Drag an appointment into somebody else's column and it moves. Click one and it opens. The engine will refuse anything that cannot actually happen.
It books everything the job needs at once.
Not a time slot. The person, the room and the equipment are held together, so the diary above cannot be double booked by anybody, including you.
The gap in the middle belongs to somebody else.
A colour develops for forty minutes. The chair stays held and the stylist does not, so that time is offered to the next client rather than lost.
Blocking time never cancels anything.
Mark somebody off sick and it tells you how many appointments fall inside it. It will not quietly bin them, and it will not pretend they were not there.
Online booking is a feature of this diary, not a separate thing. See the page your customers book on and watch it land here.