One thing that has been bugging me for a long time with LibreOffice is how docked contextual toolbars (ex: if I click on an image and the image controls toolbar shows up underneath the main formatting bar) just show up abruptly without a transitional animation for the UI. When running the GTK3 version, I would like those UI elements to slide out smoothly, like what we see in GNOME applications. One way to do this would be using this container: https://developer.gnome.org/gtk3/stable/GtkRevealer.html
Ok -> NEW
they are not real gtk3 toolbars, they are vcl ones themed to look like the gtk3 ones
If we get around to using native components in toolbars then this could fly, that that's a long way out for now