Using external microphone in Bootcamp
The short answer is sorry, but there seem to be no driver to support the external input in the headset. My solution that works is to get a cheap USB to headset audio adapter that support the 4 pin 3,5mm jack of the headsets. Here is one that works, but you can surely find others in your local market:

https://www.wentronic.com/de-en/index/artikel/USB-2-0-sound-card-audio-adapter-headset-adapter-96291