How do Zoom while B-spline tool in use

I have started a B-Spline draw, and have entered a number of nodes, and desire to continue the draw operation.  I would like to Zoom in or out, without leaving the B-Spline.

Is there some mouse or keyboard shortcut that will zoom in or out?

I do notice that if I move the cursor out of the drawing area that the drawing area auto-scrolls so the cursor is again in-view, and I may continue with my B-Spline.

But how to zoom B-Spline while the tool is active?

I do know I can exit the B-spline, zoom the drawing, then re-enter the B-spline and pick up where last point was placed, but how to zoom without leaving B-Spline?

Thanks in advance.