One way is to have a loader project load other projects via iframe.
But that doesn't really fix the issue of needing to have multiple projects to maintain.
I would like to have everything in one project and be able to decide what is included in the final build.
Essentially how it is now (or at least how I understand it), even if you have a project with extra layouts for testing, future expansion or work in progress, all these layouts and the belonging code will also be included in the final build/export - that is not really handy.