As @JB3DG mentioned you need to create a $texture and then reference it in 3DSMax. I have not done it myself, but it seems to workFirst of all many thanks for the many answers and the many good tips
Now I've come a step further and can say that my idea of raindrops on a windowpane of a BGL building probably does not work. The corresponding section in the SDK to the Mooney Bravo, I have now read several times and it follows that you need two models: external and internal. The windows of both models (internal / external) need different material settings. For this I had specially created a vehicle (Hummer H3) to implement there the WindShildRain effect. That did not work out, but I'm on a good way.
Thanks again to all!