I have a CMake-based project that can be configured as follows:
- build everything (host application + library, default)
- build the host application and associated infrastructure only (a bit like VLC)
- build only the library (think libVLC)

At the cmake level this is implemented very simply with add_subdirectory() calls that are or are not made.

What I'd like to be able to do is:
- maintain a single source directory
- maintain 2 (out-of-source) build directories, one for the host, one for the library. There are good reasons why I want a separated approach like this, instead of using a single build directory and telling make to build only a specific target.

I'd then like to open projects for both in a single KDevelop session so that I can edit files from both parts of the actual source project with full parser support.

This turns out to be very tricky. It seems that the CMake project manager maps a given open file to a given session project by matching the project toplevel directories to the file path on a first-come basis. 

Currently there's only one way to achieve something more or less what I am looking for, and that's by adding multiple build directories to a single project. That'd work if
- cmake weren't invoked automatically each time one changes build directories
- changing build directories were possible without diving into the project configuration dialog. Ideally there'd be a pop-up menu (or contextmenu submenu) for each file that's part of a project that lists the known build directories that build the file in question. I think that information is readily available from the compile_commands.json files from the build directory roots.