Counterpoint exercise with whole note under half note in same staff

I’m doing a counterpoint exercise for 2-1 and following along this video: How to Compose 2:1 Counterpoint || Tonal Voice Leading 2 - YouTube. Is there a way to put a whole note under a half note in dorico? Or do I have to break this out into separate staffs?

Just create another voice. While in note entry mode press shift-v. Thereafter you can switch between voices using v. (The little note symbol at the bottom of the caret will tell which voice you are currently entering).