Removing the ghost rests of Voice 1

Hi all,

I'm writing an 4-voice, two-stave organ part. The upper stave, with voices 1 & 2 is fine. The lower stave has become a mess because I accidentally started entering notes as voice 1; but now that I've deleted those and then done voices 3 & 4, I'm left with a whole lot of voice 1 rests in the score. I've rendered them invisible, but of course they still show as grey in the software, which is distracting. How can I completely remove voice 1 from the lower stave, or make that voice completely invisible?

I didn't find any helpful advice on the Voices page of the manual.

Thanks.