I did this earlier, then thought, better wait for the official Ofnuts.
This worked here and looks like your intention : caveats: linux installation and I use _alt instead of _storage (It is an old version

) Use whatever is already there.
addonCollectionManager.ini
In the first section
[ all ] changing the location addons_stored
from
addons_stored:{GimpUser}/{type}_altto an explicit path.
[all]
# enable:brushes dynamics fonts gradients palettes patterns scripts
enable:brushes fonts patterns scripts
addons_active:{GimpUser}/{type}
addons_stored:/home/rich/gimp_stuff/{type}_alt...
...
.etc.