In the context menu under Source there is an option to automatically format/indent code, but it doesn't have a keybinding associated.
The command also doesn't seem to appear in the Window → Preferences → General → Keys menu.
I tried editing the plugin.xml file in
eclipse/plugins/com.wolfram.eclipse.MEET_10.1.757 as described here, but to no avail. I'm not even sure whether that is the correct file to edit and which command id to use.