What's the intersection of "users who want to delete a specific cookie" and "users who cannot open Developer Tools"? For the average user, deleting all of a site's cookies seems like all the granularity you need (and will be a more effective troubleshooting tactic anyway).
I don't think many non-developers use the dev tools for tasks, while people merely interested in technology (gamers and such) will get a gentle introduction to how cookies work from looking through the cookies in the normal interface. Those people might go on to become developers eventually.
Effectively zero. Ridiculous that anyone would think this an issue even worth discussing.