Because you are new to the forum, and like everyone without trust level, you can’t post links, so we can avoid spam, so moderators do not work 24-7 like mad mans.
Was answered already
Here is how you can go around it was mentioned above.
is xdg-desktop-portal-gtk or xdg-desktop-portal-kde or xdg-desktop-portal-gnome and i think (might be wrong) that you actually need the first one and make sure the service is running.
Well, is a community edition and a lot of changes happened due to the Gnome changes, but not all of them got addressed … This might be one of those issues.
There are only stored the bookmarks for the native gtk file dialog, but if something else is shown as file dialog, then those do not help much.