The following works for me in Cubase 11 Pro:
- Enable Input Transformer for the desired track
- Enable Module 1
- Add in the Filter Target section
- Type Equal Controller … And
- Value 1 Equal (1 for Modwheel, or any other desired CC number)
- Add in the Action Target section
- Type Set To Fixed Value Aftertouch
- Value 1 Use Value 2
- At the bottom choose Function Transform
To reuse this Input Transformer configuration in the future, save as a Preset (I called mine "ModWheel to Aftertouch, since I used CC 1).