( Alas just like my last reply; I'm time limited, so I'll provide a quick response only here, it maybe thus somewhat limited ; or need clarification like I had to do last time )
I gave a response to a question on a question on seed that may help you at
All Ubuntu and flavor ISOs are built by the same tool; the seed file just tells them what packages are to be included which creates the differences between say Ubuntu Server, Ubuntu Desktop, Ubuntu-MATE, Lubuntu or a Xubuntu-Minimal ISO. In effect the seed files dictate what gets put on the ISO (packages; latest being used usually, with some control beyond that for snaps), the result can be read in the manifest file when you download it much later (all package versions listed here).
The seed files are used by Launchpad, so I doubt they'll be useful anywhere else; they do help you understand the Ubuntu ISOs though.
- Seeds - Ubuntu project documentation
- Seed management - Ubuntu project documentation
- SeedManagement - Ubuntu Wiki
There are some docs I'd like to use, but I'm out of time currently sorry....