Toggle it on/off with: Edit > Advanced > View white space
The default hotkey is usually ctrl+E,S (I think this is for General or C# developer settings)
If you use Resharper, you may find you need to use ctrl+R,ctrl+W (this may also apply for C++ developer settings)
(Note that the hotkey may be different for different key binding schemes, and can be customised in Tools > Options > Keyboard. Also, Addins and Extensions (e.g. Resharper) may modify them or add their own equivalents. But the bound key will be displayed on the above menu so it’s easy to determine what the hotkey is on your PC)