ProBuilder Won't Let Me Expand Pre-Existing Cubes

Hi,

I am trying to follow a tutorial from the Unity fundamentals package that came with the Unity Plus membership, and I am trying to use ProBuilder to expand out a "bridge" by holding down shift and dragging out the selected faces. Instead, what's happening is that it's creating a ramp. See the video below for what I'm trying to do, versus what's actually happening:

Thanks!

 

Update: I found out that you can extrude the faces in the ProBuilder UI, but I want to be able to do it so that I can click and drag it in the editor itself. Anyone know how I can do that? On this website, it says that I need to click and drag with shift, but it's still not working. https://unity-technologies.github.i...probuilder/probuilder2-gh-pages/toolbar/face/

 

Looks like the extruding itself is working, but the two dragged edges got somewhat merged into one. What happens if you try to separate them? Are they already completely collapsed or just at the same position?