to RedHeavenHero: Ah, if only I could extract these videos from the mod for all campaigns and check them in the editor...
But I remember that my campaign never lagged...

to Juss456: You can do it, and it's not very difficult. Just open the folder with the map using WinRAR, find the map.xdb file there, open it with Notepad (it loads for quite a while), use the search function to find startScene - enter the link to your video. Then: open the map in advanced mode, click refresh tables, ---> the video will appear...

Added 2 minutes ago