Documentation for how custom maps have been made?

[ItAvvy]

I saw recently that JezuzLizard and EvelynYuki (account now closed?) made a full from the ground up custom map using OpenAssetTools. I was looking into both that and the custom map tool made by CraftyCritter as a potential pathway to backport bo3 maps into bo2's engine (mainly as a method to "recreate" the unreleased DLC5).

However, I've found almost no documentation on how they managed to edit/create a ZM map in any meaningful way, and discussion on how the larger mods have been made seems to be rather difficult to find. How to get the maps into something like blender seems to be undocumented. Is there a larger repository where I can locate all this information? If not, would anyone be willing to work through the process with me on some level?

My thought process was: Extract map files from bo3, open the map in blender, export it in a way that CraftyCritters custom map program can handle, and then somehow combine that with OAT to rebuild the zombies functionality from the ground up. But sadly, outside of just tinkering with files for hours on end it seems there's no elegant way to really learn any of the information needed to have a clean workflow here.

I have very little experience with 3d modeling, but would consider myself to be a competent programmer. I just tend to struggle when left to figure things out on my own.