I cannot find the UI to disable the Alt+mouse wheel feature that triggers zooms. I believe there should be a UI option within the xfce4-accessibility-settings UI. If the feature requires Xfce4 compositing to run, then the a11y UI should set the checkbox to insensitive and contain a label below that reads "this feature requires the Xfce4 compositor to be enabled" (imo, in italics to indicate it's a comment rather than "content", with Xfce4 compositor being a clickable link that launches the Tweaks UI).
Created attachment 5811 Add a zoom_desktop xfconf setting This only adds the xfconf setting to xfwm4. It doesn't expose it as a UI in xfwm4-settings.
Thanks, works nicely! We'll have to figure out where to add it in the UI in a second step, be it xfwm4-tweaks/accessibility or xfce4-accessibility-settings (or even both, but only shown in one place conditionally, depending on whether xfwm4/xfce4-settings is available/installed). Pushed it to master meanwhile so users can already disable the zoom-feature at will: http://git.xfce.org/xfce/xfwm4/commit/?id=fd07ce807ecd6bff0a579f416ea9425878f426cd