If I understand you correctly, you're referring to this bug report [1]. It was recently discussed on the list [2], and there is even some code implementing the feature as a plugin [3].
[1] https://sourceforge.net/tracker/?func=detail&aid=3383201&group_id=15... [2] http://www.mail-archive.com/geany-devel@uvena.de/msg05210.html [3] https://github.com/pzoxiuv/Geany-Plugins
Oh, great! Amazing that this has been worked on so recently. It's almost what I want... But I think it should be the default behavior for 'auto-close quotes and brackets', instead of a plugin. I don't think any extra configuration options are necessary - nobody would complain about it if they've already turned on the 'auto-close' feature. I also think that the actual characters are much more appropriate triggers than 'Ctrl+<key>'.
Thanks for your help! Nathan