I suggest using the Reference Index - it's designed specifically to look for any kind of symbol (class, traits, methods, vals, vars) regardless of it's hierarchical position - contrasting with the Scaladoc's left index which doesn't show inner classes, traits or objects.
Unfortunately it's only available in the nightly. You can see the whole thing at nightly Scaladoc. Notice the upper box in the left frame, above the index.
Hope it will be bundled with Scala 2.9.0.
Edit As of 2.9.0, the reference index started to be bundle with Scaladoc. No need to go to the nightly docs now.
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