Added: 4.19.0 Preview 5 version. Was tested with 4 and 6 trackers.
By the way. Unfortunately, I don’t see a plans for controllers input unification in the UE4 Roadmap. Does anybody interested in a patch for a whole VR system refactoring with unificated input from SteamVR and Oculus controllers (i.e. Touch, Vive wands and Knuckles) and support of discrete input from different Vive Trackers? My idea is to put this input to event deletages and functions inside of Motion Controller Component and send them from VR plugins via IMotionController/XRMotionControllerBase interface.