What this means is that each part can be created from scratch, like you build it in the editor, and like subassembies, you can take it and create a seperate part BUT, it merged into one piece that functions as one (like if you build a collection of parts that would look good as a command module you can build it, and then merge those parts to make a fully functional command module that is only one piece and combines the externally seen meshes into one) at least I think that way would work, I’m no game dev