I’ve already increased the distance between staff groups in Layout Options and this works fine for most of the groups, but there’s still not enough room between the vocal group (due to the lyrics) and the first violins under it. I know that I can go through each page of the score and move the string staves down but is there a way of doing this globally without affecting the other staff groups?
No, at the moment, there isn’t. Perhaps in the future we should add a further gap type for vocal staves, or perhaps an additional amount of gap to add on to whatever gap is ordinarily used at that place in the system which is only added on for vocal staves.
It’s not only the lyrics but also the generally high range of the first violins which makes the distance between those groups too small. For now I’ll have to do it manually but I hope that the possibility to do this globally gets implemented sometime fairly soon.
If you do have a generally consistent system layout, you can make the adjustment on one page and then use the Copy Staff Spacing dialog to apply those changes to other pages with the same system layout in one shot.