Three quick tricks for the DOM tree in the Elements Panel:
When you are editing the DOM as HTML (Right click > 'Edit as HTML'), use the shortcut
Shift + Tab to auto-indent the markup. Works on single lines or multi-lines.
Get the corresponding CSS selector for a DOM node: Right click >
Rearrange the DOM with a drag-and-drop action in the DOM tree. Useful for quick prototyping of alternative layouts.