Creating custom map preview in World editor

[udg_Potato]

I've been trying to do this but ultimately to no avail.

I've seen for example that this map has it in perfect quality (Frostcraft) so I'm wondering how is this doable?

https://imgur.com/a/6sVmsyy

Thanks for the help!

PS - Ive been on this forum since 2008 but haven't visited it in like 10 years!