Please give the option to hide bookings calendars from the GAL. Multiple options are needed: >hide during creation by users. >hide by admins individually or in bulk. >default org wide policy to...
You can hide automatically by changing the GAL filter :
https://learn.microsoft.com/en-us/exchange/address-books/address-lists/configure-global-address-list-properties
And exclude mailbox with RecipientTypeDetails = SchedulingMailBox
You can also make a script that hide them.