At the very least, this doesn't work at all in Haven.
And the manual doesn't help with this.
The maps folder, which is packed in the datapack, doesn't contain ready-made maps. That's the first thing.
Secondly, as the author of the topic already wrote, the drop-down list where missions should be added to the campaign is empty, even though the maps are single-player maps, specifically for the version that is installed, and they are located exactly where they should be.

So, the question remains open and unresolved.

If anyone can help, please do.