Gtk.Dialog unable to remove Buttons on bottom
I was trying to reproduce Gtk Dialogs, which do not have buttons button, but in the Gtk.HeaderBar. Even on manuall change in the xml file, Glade tries to return the action area back.
I was comparing mine source code to: https://gitlab.gnome.org/GNOME/gnome-control-center/blob/master/panels/printers/new-printer-dialog.ui And mine code (probably non-valid, but openable in Glade 3.32.2 Nightly Flatpak)
Hope this helps by development. :-)