AdventureWorksLT might look like a good database to get started with if you want to look at the GenDotNet tools (they are still in a very alpha state), but its not. The reason is the use of multi-part primary keys. I don’t know how much to support these in the tool, so for now they just aren’t supported.
The underlying question is whether your many-to-many tables should have their own primary key and use the parent primary keys as logical keys, or whether the parent primary keys should be combined into a multi-part primary key. Because my many-to-many tables often have, or evolve into having a payload, I use the first approach. The second becomes relatively complex at a number of points in the generation process.
If you feel multi-column primary keys are tremendously important or valuable, I’d love to know why.
For now, multi-column primary keys and tables without primary keys are simply not supported.