The string you need is: –user_data_location=”path”
Since a few versions ago of Football Manager they have for some strange reason removed the option to change the fm20 folder and drive on your computer where games is saved and where you put any external graphic that you might wanna use like face packs and logo packs.
You can still change it from outside Football Manager 2020, this tutorial will show you how.
This guide will also show you where to find your fm20 graphic folder, the Football Manager 2020 graphics folder location and where to find your fm20 save folder, fm20 save folder location.
In other media
How to get graphics in FM20: