I think I can already can guess the answer but is there any support for concurrency for multiple users? My simple testing tells me the last person to press the save button will have their changes saved. If someone has made a change before the save is pressed then but after the edit form was loaded those changes will be lost (i.e. no optimistic locking).
I'm guessing this is probably out of scope as I don't even think WordPress has any sort of locking either, I might be wrong though.
Kind of related, the user has asked if there could be some sort of auto-save so they don't have to always scroll up to press the save button (it's a long form). I was thinking I could maybe add some javascript to press the Save button but not sure what kind of grief that might cause.
In the backend, WordPress supports a feature to notify a user to take over the post-editing of another user. Please read more on the documentation https://codex.wordpress.org/Post_Locking
Yes that looks like what I need. Are you saying custom table should already have that support as well or would I have to change it to be a post to get that support?