Hi Caolan753
i use this script (sorry, I don't know where I found it anymore so i reuploaded it for you)
Link: https://havenith.nrw/lss/hiding.user.js
This script is in german but not hard to use
Click on the arrow and then on "Beteilligte Verbands Missionen". All alliance missions where you have vehicles are now hidden.
I hope that can help you