What is GlideOverlay

I was on twitter and this came up;

Try GlideOverlay instead. I can send you a DM with some sample code.
Or ping on SNDevs.

--- Jonathan Jacob (@TheBurgerlution) July 24, 2019

I had to make a page for it.

It appears to be a undocumented modal.

It's used throughout ServiceNow on VTB, Change, and Surveys.