How to name a deskop in mission control? I have multiple desktops. I want to be able to name them. Is it possible out of the box? 

Or at least does MacOS have API for that? I'd create an application.
You cannot rename desktops in Mission Control.
You can’t rearrange or rename Spaces, either.
You get Desktop 1, Desktop 2, and so on, and that’s it.
This Thread should give you more information.