Could you resolve the issue? You can change the path via the FAF client.
If you get the error message, when you click on "Choose...", then a possible solution could be to re-create your initial folder structure, and then start the FAF Client to change its path, before you move/remove the old-map-mods-folder.
C:\Users\magne\OneDrive\Documents\My Games\Gas Powered Games\Supreme Commander Forged Allianceimage.png