Second/Third/Fourth Voice Full Measure rests in non 4/4 time signature

Place a rest of any length in the measure with that voice in question. Click that rest, and press ctrl+shift+delete. Voila, full measure rest in any voice, for measures of any length.

Make sure that you click the first rest in the measure, if multiple rests appear (such as if you add a quarter rest in a 3/4 measure; three quarter rests should appear. Click the first rest).

Easiest way imo is to use the switch voices command twice.

Fwiw, though, note that depending on the context, there may not be any need or advantage in showing these rests. Normally if a voices rests for a full measure or more it isn't shown, except in cases where it might cause confusion. Again, it depends on context.