Key Bindings allows us to customize the Xcode functions to keyboard command keys.  I've know about this customization for years... and assumed just learning the few short-cut key strokes as I go would be enough... no need to remap the key strokes and get non-standard behaviour.  But then I saw a remapping of (command)P to refresh the preview canvas.  This is something that is very useful and not defined in Xcode.

So that got me looking... I bet there are other key bindings that are useful... but are not in the standard Xcode key bindings.

I found this article and video that shows me how to not only add a new key binding but to add a new function - such as "duplicate the current line of text" and then bind to a key stroke.

Custom Xcode shortcuts - Bits on Software

Xcode Tips and Tricks: Custom Shortcuts that will Change Your Life Forever!

Now I have these new Xcode key bindings to functions that Xcode has never had.

Delete current line (control)(shift)K

Duplicate current line - down (control)(shift)D

Insert new line - below (control)O

Insert new line - above (control)(shift)O