Hi, it’s me again: Frank from Germany. 
// I have a question: When I import a plant from Megascans via Transmutr to SketchUp: Is a translucency map used for the foliage? If so: Where can I find it in the VRay-Options? Thanks! Cheers! Frank
Yes, if a translucency map is sent by Bridge, it will be used by Transmutr.
You should find the translucency map in the V-Ray 2sided material.