Create bookingStaffMember also requires Add-MailboxPermission

I created an Entra application with the required Graph permissions to manage Bookings scheduling mailboxes so that I could update the staffing for a Bookings page that I'm not a staff member of.

Using that application to request a Microsoft Graph access token, meant I had the required permissions to add a user account (that already had a Bookings license) as an "administrator" (role) for a Bookings page (Bookings business), to replace another person who was the previous Bookings page administrator, but who had since left.  I used https://learn.microsoft.com/en-us/graph/api/bookingbusiness-post-staffmembers?view=graph-rest-1.0&tabs=powershell to do this.  For the record, I was not able to do this using https://learn.microsoft.com/en-us/powershell/module/microsoft.graph.bookings/new-mgbookingbusinessstaffmember?view=graph-powershell-1.0 using Microsoft.Graph.Bookings module version 2.30.0, presumably because I am not a staff member with the Bookings "administrator" role for that particular Bookings page.

However, the newly added user could not access that Bookings page at https://outlook.office.com/bookings/homepage until a further step had been completed (Error: "You don't have access to this booking page" shows instead).

To ensure the new Bookings page administrator could access the Bookings page, I needed to add mailbox permissions, which I used https://learn.microsoft.com/en-us/powershell/module/exchangepowershell/add-mailboxpermission?view=exchange-ps for.

I found that giving the new Bookings page administrator full access to the scheduling mailbox ensured they could access the Bookings page.
Example using ExchangeOnlineManagement PowerShell module: Add-MailboxPermission -Identity email address removed for privacy reasons -User email address removed for privacy reasons -AccessRights FullAccess

If there is a more efficient way for an system admin to add new staff to a Bookings page, please let me know - otherwise, hopefully this helps someone who gets stuck 😊