<kbd>⌘ Command</kbd> + `Double-Click on a symbol`: Jump to Definition of a symbol.

<kbd>⌥ Option</kbd> + `Double-Click on a symbol`: Find Text in Documentation of a symbol. (Only works if you have they symbol's Doc Set installed.)

Favorites Bar:
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Favorites bar is just like you have in Safari for storing - well - favorites. I often use it as a place to store shortcuts to files I am using right now. Generally this is more useful when I'm working with a large or unfamiliar project. 

To show the Favorites Bar, select the following menu option:

 - `View` > `Layout` > `Show Favorites Bar`