Instead of multiple nodes for LeftShift, RightShift, LeftControl, RightControl etc why not make a single node for Shift and Control and then include checkboxes to select Left or Right inside Details panel?
When control, shift, and alt are being used as modifier keys we always consider right or left to be the same, however, if you are binding directly to the key we expect that you would rarely want to consider them as the same thing.
Keeping the input key nodes consistent regardless of whether it is a key that has a right and left version on the keyboard or only a single instance is really just easier and thus why it was done that way.
In the next beta release you would have the ability to write your own custom blueprint nodes that do the kind of expansion that would be necessary to accomplish having a checkbox and it would be viable to create a plugin that adds a node of this type if it would be useful for you.
Good to hear we would be able to write our own BP Nodes next time. 
Any ETA on when it would be available?