I'm trying to use Dolphin as file chooser for Firefox in Archlinux instead of Nautilus. I've read this but it did not solve my problem. The config seems related to firefox as xdg-mime query default inode/directorydolphin.desktopWhich is right. Also cat /usr/share/applications/mimeinfo.cache | grep  x-directory/gnome-default-handlerx-directory/gnome-default-handler=kde4-dolphin.desktop;Seems to be right too. What am I missing?
Set new default file manager for firefox in Archlinux
arch linux;firefox
Type about:config in the address barSearch for ui.allow_platform_file_pickerToggle it to trueRestart Firefox.