Hi Manu,
I presume you mean single line staves for percussion in your first comment? We’ll investigate further.
Aside from that, as you discovered, repeat markings in the Score will not have any impact on playback in the rest of Cubase. This brings a lot of complexity, and I’m not sure if and how we could do that. It’s certainly not a minor bug, but behaving as designed right now. You could look at hiding the notes (score menu) in the repeated bars.
There is a separate thread concerning Omnivocal Lyric integration here: Omnivocal -- how to enter lyrics