Inputting the 2nd Lyric line and then editing it to be a translation 2nd line forces the lyrics into the middle of the lower staff in Galley view.
I should have pointed out that it isn’t consistent.
in Galley view, Dorico does not its “magic”, the staves are spaced equally, whatever the lyrics you might input. As I only work with opera scores, I have taken the habit to widen the percentage, in Layout options, Vertical spacing, “In galley view, expand ideal staff gaps to :” from 125% to at least 160%
Hope that helps !