Ability to nominate an appointment type as "Invoice Not Required"

In settings under “Edit Appointment Type” it would be useful to have a section to mark as “Not For Invoicing”.
Examples: Staff meetings, development sessions, holidays and a variety of other appointments that do not require an invoice to be raised.
These appointments can be set as “unavailable time”, however, for ease we have created them as their own appointment types and colour coded them so it would be great to be able to mark these as “invoice not required”.
When we raise a report of “Uninvoiced appointments” all of these appear on the report and it would be more efficient if they didn’t.