[Replace the ALT key with CTRL]

In case this helps anyone, in Affinity Designer 2 there is an option in Preferences > Tools for "Zoom with mouse wheel". If you turn this on, the canvas zooms when you roll the mouse wheel without any modifier key.

If you subsequently turn off the "Rotate canvas with Alt key", then you'll effectively get zoom while alt-scrolling (even though the alt is not needed.) It satisfies the need to work this way.

Using it without a modifier key is like hooking up ChatGPT to the hoist in Image A by Frank above