This is not a CLR-based nor JVM-based IDE, but it is otherwise a nice lightweight IDE. The editing component is based on Scintilla.
A similar kind of IDE would be CodeLite.
Geany has a bona fide manual that you can quickly skim through to get tips.
1) Under Menu > Tools > Configuration Files > filetype_extensions.conf Add this under [Extensions]:
2) Put filetypes.Cobra.conf in ~/.config/geany/filedefs
3) Choose Menu > Tools > Reload Configuration
Note that this currently uses the "Python lexer mode" for Scintilla. Although not perfect, it's not bad. We could use a lexer mode for Scintilla which would then get reused in multiple projects.
If you don't see syntax highlighting for a Cobra file, it's likely because you opened the file before setting up Geany for Cobra and now Geany is stuck on that particular file being an unknown type. The solution is to execute step 3) above.