Guidance bar numbers at the top of the page (in the grey boxes) are handy to have, to navigate a score being written into.
For large orchestral scores, is it possible also to show guidance bar numbers above a lower stave (e.g. above the strings), so that one does not have to keep scrolling to the top of the page to see which bar number one is writing into?
The grey bar at the top is called the system track.
You can show bar numbers at multiple positions in the system, although that affects the resulting layout. You can also see guide bar numbers above each staff, which is a visual aid inside Dorico and is not printed/exported.
Evansf, to give you a visual example to what Lillie has explained, here is Galley View with visible system track and with visible guide bar numbers (above each staff and each bar):
Learning, learning, learning. Thank you so much Lillie and k_b. 
Hi,
Is it possible to have the guide bar numbers on selected staves, for example on top and bottom of strings and/or brass etc. Having numbers on every staff and every instrument looks a bit clattered, thanks!
No, at the moment, it’s all or nothing.
