an idea for embedding dash-to-dock in the top bar

You may or may not have considered doing this already. I don't consider this complete. It is just something that works for me (not fully but good enough). 

I simply reoriented and re-parented the elements so that they at the centre on the gnome-shell top-bar. I prefer this layout because it saves space and top-bar is closer to the regular window controls and tabs and title bar etc. So placing the dash there seems more space and movement efficient.