As it is for now there's no easy way to change a folder's icon with a custom one. Exampel I want to change my Steam folder which indicate it's Steam in that directory. I have tried with gio command also with gvfs-set-attribute command but it is deprecated.
gio set -t string metadata::custom-icon file:///home/orion/.icons/ePapirus/48x48/places/folder-black-steam.svg
But it didn't work. Is there a way to use custom icons in "Files"?