If you need to add specific context for Linux machines and another for Windows versions, but test case itself should not be different for both the Linux and Windows machines, you can use different projects with the same name and same IDs of contexts, the difference is only in location.
Do the following steps for that purpose:
Move all platform dependent test contexts to a separate project.
Copy project on filesystem (don't use RCPTT IDE during this step. If you import both projects to the one IDE, an error will appear because of the same IDs of contexts. )
Change all contexts to handle another required platform (do not create new contexts, edit them in-place, do not change name of project)
During build supply different context projects using either "Extra projects" option of RCPTT Maven plug-in or directly replacing project with needed version in your build script.
The main idea of this approach is to get two different sets of context with same IDs so that tests reference them in uniform way on every platform.