Editnotices for pages are not currently exposed in the API, but are expected to be used by any interface of a Wikipedia editor. This implies that the information should be easily retrievable.
It should be noted that the VisualEditor api has it's own private implementation of listing all edit notices that should be presented to users: https://en.wikipedia.org/w/api.php?action=visualeditor&format=json&paction=metadata&page=List_of_emoticons&uselang=en&oldid=846338965
This should probably be moved to core as well as be exposed via restbase or something similar.
Version: 1.21.x
Severity: enhancement