Two crazy days of my spare time, I was coding between sleeping and eating, with a lot of cups of coffee. Now Scala plugins support Go-To remote declarations (CTRL + Click on var/function name), and when you put cursor on the identifier name with CTRL pressed, or under auto-completion, the doc will also be shown as tooltip.
These features work for Java classes too with a bit poor performance, I'll fix it later.
Not all identifiers have been type inferred, so these features are not applicable for all identifiers.
Please update to Scala Editing module as version 1.0.26.xxx when it's available, which is the only stable one these days. Remember to unzip Scala lib's source under $SCALA_HOME/src