After you clicked on the endnote feature did you close InDesign and reopen?
These are IAMs(In app messages).
Closing them once, will disable them unless you clean your cache and preferences.
"Closing them once..."
I realise I'm just a stupid Adobe user, who's been a user since adopting Pagemaker in the '80s, but I would expect an 'X' or a CLOSE button, but sadly the geniuses at Adobe forgot to include it. Eiterh than or a DISABLE MESSAGES option in Preferences. This stupid little bug cost me an hour of productivity; half an hour trying to rid myself of the damned banner and half an hour on the Internet searching for an alternative to InDesign (which I've been using since version 1, BTW).
Not good enough Adobe.
Hi, my blue banner is definitely closable but it turns up now and then even though I've closed it before. I haven't trashed my prefs.