I really like the Highlighting of HTML tag tree feature to visualize structure of HTML by using nested color bands on the left (see screenshot):
It would really help me read existing code to quickly see the boundaries of the current object inside nested if-else blocks inside callback function that is inside a function call with multiple functions as arguments... that kind of stuff.
(no need for the navigation pane at the top, just nice nested colors on the left)
P.S.: I am using IntelliJ IDEA 15, but as I understand it all web-related features come from the WebStorm community...?