TerraTela

Most of what it expands on is not what you see in-editor. It's the application in the 2nd DOOM window. Fullscreen is bugged when using the Vulkan graphics API, where changing windows often causes the game to crash. Based on you mentioning "needing to be in windowed mode", I assume you had read the installation instructions in the Guide to SnapHak document, but if you read further along, it goes into an in-depth explanation in many of the capabilities of the SnapHak tool. In short, it's a glorified text editor that lets you manually enter data in the properties of an entity, which takes away the limitations imposed by the in-game editor, and instead lets you work within the confines of the entire engine. This differs from modding, in that it makes no changes that would require anyone to download a mod to play it. Even console players can experience the map changes made using SnapHak. The "broken" object you saw is actually an unknown entity template that can be used as a base for placing entities in the map that are made available just by the game's engine itself, even if not made to be in placeable in SnapMap.

I made a map called "Cvar Resetter" for cases like this. Map ID for it is 48SUJR4A. (I see you found that map yourself but I'll leave this here for anyone else who checks this post) Typically, maps that override these values either reset them when you beat the map, or the map is still a WIP and doesn't have that set up quite yet. But there's not much a map author can do if you leave a map early as SnapMap logic can't trigger off of that.

Main reason I prefer Discord is that the live chat aspect to it means I can more immediately address people's technical questions as they come up. It also feels less social and active to talk back and forth through delayed responses like a forum setting does, which is also why I don't really do much on the SnapMap subreddit that I also am an admin for. It's just a glorified billboard to direct people to the more active and maintained Discord server at this point. And as far as I know, there's just the one remaining SnapMap-focused discord server that I run, not really scattered across multiple different places.