Have you tried mSLDev?
https://forums.mirc.com/ubbthreads.php/ubb/showflat/Number/241147/It can only collapse the entire alias/OnEvent/whatever, not sections inside of them.
Development has stalled so anything added after December 2014 (like "on *:PARSELINE:{}") will give errors.
The download link on the front page has a version from March 2013.
If you want to try the latest version from December 2014:
http://msldev.com/download/win/latest_build.zip
