Self-descriptive: When creating or editing a page, if you were to press escape, it would close the overlay.
Weird, just checked this out and ESC works fine in the Sitemap with an opened Page (Mac)
Could you please tell what are your OS and browser?
I tried to replicate it, but ESC is also working fine for me. Ok to close ticket. (Windows 10, Chrome latest version)
It seems our “ESC-hotfix” is working