If this is only due to the fact that you registered the structure of the control systems, variables, etc., you can create a diagram in another place (for example, Dia, XFig or Inkscape, if you want to use open source tools) and implement them in the Doxygen documentation through the image, the keyword from your code:
To do this, you need to specify Doxygen in the Doxyfile where to find the images, and place the images relative to your doxygen path (DOCROOT / images in this case):
Using latex extensions or other language-based graphical markups to generate graphs from the Doxygen doc does not make imho justify the overhead of learning a language, establishing and aligning a tool chain. On the other hand, if you already have a tool that automatically generates a chart (from your code or configuration file), there must be a breeze to run the tool from the Makefile, let it generate an image and embed the image in your doxygen doc via the image keyword.
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