My [reply](https://github.com/geany/geany/pull/3377#issuecomment-1713642517) to @farvardin noted that Geany does not import the optlib directory from ctags so Geany probably does not support optlib parsers directly.
@techee should comment on if the C file generated by optlib that I see is part of https://github.com/universal-ctags/ctags/pull/3812 can be directly used by Geany, that is beyond my pay grade.
But in general regular expression based parsers have not been used in Geany because of concerns about speed. The parsers have to run between keystrokes, it would not be a good user experience if they caused significant delays.
This concern may be misplaced, how do they compare to the C/C++ parser?
The C/C++ parser does not seem to cause issues even with files of several thousand lines.