How to use schemas outside the container in flatpak

I want to use the org scheme.gnome.desktop.app-folders for displaying user folders. But when launching the application using flatpak, the list is empty. How do I do this correctly?

You can’t, by design.

Except there’s the Settings Portal. For GNOME there’s a small set of schemas that are made available for sandboxed apps throughout the portal. See src/settings.c · main · GNOME / xdg-desktop-portal-gnome · GitLab

That doesn’t include the app-folders gsetting you want to access, and I don’t think there’s any interest in allowing that tbh.