I thought originally that this would look out-of-place in a gtk-based environment, but this seems to be a common paradigm for gtk apps as well (see here), and I think it would be a useful feature -- at the very least a potential customization option.
Even having icons in the sidenav widget seems idiomatic for GTK/Gnome. See for instance the "patterns" app showcased here.
I thought originally that this would look out-of-place in a gtk-based environment, but this seems to be a common paradigm for gtk apps as well (see here), and I think it would be a useful feature -- at the very least a potential customization option.
Even having icons in the sidenav widget seems idiomatic for GTK/Gnome. See for instance the "patterns" app showcased here.