With doxygen, one can add extra, non-source documentation file, which contain doxygen blocks just like a source file - for "out-of-place" documentation. See this example in the doxygen documentation, or this question here on SO.

I use CLion (2026.2.3) with a certain (C++) project, to which I'm adding some documentation in a .dox file (since it doesn't fit in any of the actual source file). Unfortunately, CLion It doesn't recognize a .dox file type, and doesn't highlight the contents of such files. If I force CLion to treat those files as C++ sources or headers - they're still not part of the project, and the doxygen comment blocks are highlit as plain comments, in a different color than doxygen comments and without keyword highlighting.

Is there a way to get CLion to property highlight my .dox files?