Hmm. There still seems to be a problem. The relevant lines of my sketch are here. As mentioned here, Inkscape allows for Shift + Wheel Up/Dn to work as wheel left/right, and since the horizontal wheel keys aren’t working right now, I figured on using the substitute…
But I find that on pressing the wheel left macro (which is Shift + Wheel Up) the display actually goes to the left and up and likewise on pressing the wheel right macro (which is Shift + Wheel Dn) the display actually goes to the right and down.
It would seem that the mouse report is getting sent twice, once with the modifier and once without?
(In the case of Ctrl + wheel, since zooming in/out changes the centre of the picture, I wasn’t earlier able to identify the extra scroll…)