I've been an active Evernote user for over a decade (since 2009), including sometimes having additional paid accounts at work. I see the oldest request for this feature is dated 2011. The thumbnail functionality has annoyed me the entire time.
If you hold out for another year, you'll make it a whole decade of ignoring a very sensible and straightforward feature request from your users. As a software developer, I am aghast.
I've stopped recommending your product to other people.