It would be nice to see if this could be revived - its a simple and key bit of functionality for any mobile app like this that has potential long lists of entries (and it’s present in most , if not all, of the competitor’s mobile apps from what I have experienced or have read). There is an existing FR from prior to this discussion still open for it: An alphabetical jumplist - what are the chances of a revival?
It ideally would be great if it also addresses the similar keyboard alphabetical jump functionality described here: Jump to location in list? (and FWIW in my recent post here: Alphabetical Fast Access In Item Lists).