Calendar availability timeslots need the option to use Custom Values.

Scenario

You're an agency owner who has a snapshot that has calendars in it. You get a customer and they receive your snapshot/calendars. If the customer edits the available times in the calendar settings, and then you push a snapshot update to the calendars into the customer's account, the calendars will then reset the available times to the defaults in the snapshot.

This is a pain and a technical oversight. If a customer adjusts calendar availability settings, these data fields should never be overwritten by future snapshot updates. But the best way to solve that is to simply allow Custom Values. If the CV is empty, then the availability for that day is simply blocked off entirely. Easy peasy.

Also, the same applies to the Custom URL field. That should also never be updated again after it has generated. However, currently, if it is updated by a customer, it will get overwritten by a snapshot update.