Can microbundle be used to create subpackages?

Currently I have a package `@namespace/package` built using microbundle. I want to store certain functionality in a subdirectory of the package e.g. `import { ... } from "@namespace/package/subdirectory"`. An example of this would be the way importing now works for Apollo Client 3.0: https://www.apollographql.com/docs/react/migrating/apollo-client-3-migration/#apolloreact-testing

Is this something that can be configured in microbundle, or does this require something else? I'm not even sure what structuring your distributable like this is referred to, and haven't been able to find anything from my searching on Google.

Sorry for my ignorance and thanks for any help 😊