On further inspection, I think part of the issue is that the source files for my main project don’t reside in the same folder as the project file (.vcxproj), nor in a subfolder beneath it.
However, in the new test project I created, the library source files are not grouped in folders, which makes quite a mess. In fact, I suppose the cause is the same as I described above – source files located not within/beneath the project file folder.
Is it possible to show some of the organization with such files? If so, is it desirable?