You can use isTagExtraBitMarked() declared in ctags:main/entry.h to detect whether a tag is anonymous or not.
As the extra parameter, use XTAG_ANONYMOUS declared in main/entry.h.
Yep, I'm aware of that and I want to address that in the future. The problem is that our internal representation of tags `TMTag`
https://github.com/geany/geany/blob/eabc09a5591e8f2efd95ca136f5870c8dcba5483...
doesn't contain a field where this information could be stored and adding more fields is an ABI change because this structure is accessible to plugins so better avoid that. But I think we could use the `pointerOrder` integer inside `TMTag` which is just some legacy field unused by anything neither in Geany nor plugins and could convert it to a flag field where information about whether a tag is anonymous or not could be stored.