The GTK file picker is hardly an improvement over the stock FLTK file picker. On windows/MacOS it's better, but with GTK you get essentially the same file picker because GTK doesn't allow icon view with the file picker, it only allows list view with a preview on a clicked on file. Why not instead allow us to compile in the qt/kde file picker for native file picker that has actual thumbnail support? People already try to use portals with GTK to use the KDE file picker.