You can automatically make member and/or contact bookings placed via the Members Portal tentative until they are confirmed by an admin.
You can easily enable this feature via Settings > Bookings and calendar settings.
Enabling one or both toggles will require an admin user to approve every booking made by members and/or contacts from the Members Portal.
Tentative bookings have a grey tab to help you spot them more easily on your calendar.
All you have to do to approve the booking is click on it and disable the This booking is not yet confirmed / tentative toggle.
You can also do this via the More actions menu at the bottom of the page.
Once a booking is approved, customers are able to edit the booking as they please.
Any new changes made to the booking won't require admin confirmation for edits past the initial confirmation.