Are the existing AVC HD content options complete?

[johnsim]

In TWG 80 2023-04-03 we discussed whether the AVC HD content options were in fact complete. For example, that Event Msg box (‘emsg’) and Edit List Box (‘elst’) were previously identified in ‘chh1.md’ but are now absent.

Edit List Box may be more appropriate for audio profiles, but are we confident that the AVC HD content options are otherwise complete?