So these instructions are with the Vive controller but I assume it will also work with other setups:
Target Tracking: When NPCs are present and you are holding a shuriken you can lock-on to specific enemies by pressing the trigger button. It will cycle through all the enemies and back to the first one while ignoring the player and any dead enemies.
To stop tracking enemies press the Menu button. If you are in the "not tracking enemies" state the menu button serves to toggle the green trail behind the shuriken on and off.
The make life easy factor:  In the .json file for the shuriken you will find the parameter: "EZscale": 5
I won't bore you with the math but the higher this number is the more likely the shuriken will track to the middle of the target's chest.
Tips:

• The module checks to see how far apart the throw direction is from the straight line direction to the target and then uses this info to project a circle over the target in which the shuriken will strike. If the offset angle is small the entire circle is within the target and you will hit the enemy for sure...if the offset angle is large the circle extends beyond the target and you can 'miss' with some probability
• Making EZscale larger in effect shrinks this circle while making it smaller makes the "spread" and therefore your chance of missing larger
• EZscale from 3-5 is reasonable and fun, 1-2 is expert mode and as it approaches 10 you can basically throw the shuriken in any direction and it will still hit its target...
• The crosshairs will automatically drop 2.5s after you throw a shuriken