Large API : Multiple YAML Files

I’m in the process of creating a large API, and i want to split it up into separate yaml files - especially when distributing to integration partners - they often don’t care about some of the modules

The challenge I have is that I cant find a way to have a reference yaml file in postman. i want to DRY it up, but am currently having to copy-paste many components into each logical part of the Api

Any help would be appreciated