Current questions and answers regarding the map editor.

Azgalor, I showed many hotkeys in the "Volume I of the Complete Map Editor Guide." For example, G disables the annoying grid. If recreating the camera didn't help, recreating everything probably won't either. But to clarify: cameras should always be created with a shutter, W.

Grigory Kovalev, create a new video in the extended editor (with Close MOD closed), save it, and close it. You can find a guide on creating videos on my channel.
Go to GameFolder/data/; there will be folders for the video you just created. Replace all of them with files from the map. That's it, you can edit. Important! After the map editor exits the "empty" mode (close mod is gray), all files remain in place and do not disappear (if you pressed Save). Then, you can move them from the data folder back into the map.
index.bin is responsible for the visibility of files in the editor.