The "sub-assemblies" button isn't available to the admin after 1 generation of assemblies

The "sub-assemblies" button isn't available to the admin after 1 generation of assemblies, even though he can create at least 4 generations. So, once he created grand-children, he can't find them directly on the admin panel. Coming from: https://meta.decidim.org/processes/supportforum/f/705/proposals/14765