So, I eventually got around to looking into it further and I suspect this isn’t news to most people, but maybe it’ll help someone trying to find similar answers:
It seems you need one (or more) of the Symbol List tmPreferences files for the language you’re using, as well as the various other files like tmLanguage, but my Ruby package was only missing the former. I had a very quick hunt and found a file which I tweaked slightly (it stripped the def prefix in the symbols list and I’ve left that in just because the JavaScript one leaves function). Then I saved the file as Symbol List Function.tmPreferences, in my Packages\Ruby folder under my Sublime profile.
[code]<?xml version="1.0" encoding="UTF-8"?>
name
Symbol List: Method
scope
source.ruby meta.function
settings
showInSymbolList
1
uuid
92E190C9-A861-4025-92D4-D6B5A24C22D4
[/code]
I kinda fumbled my way through, but hopefully jps will add a better, or more complete set, of Ruby Symbol List tmPreferences file to an upcoming build.