The ability to vertically & horizontally scroll using touchpad gestures/mouse wheel (as well as by clicking the scroll bars) would greatly improve workflow.
A two-finger swipe (both directions) on the touchpad, or any of Shift/Alt/Ctrl + wheel for mouse control seems a good suggestion.
Since the wheel is mapped to zoom, maybe Shift + wheel could be set to vertical-scrolling, and Ctrl + wheel could be set to side-scrolling.
It's now possible to define a hotkey which enables the mouse wheel to scroll the level arranger view horizontally/vertically when zoomed in.
Wheel scrolling implemented in SLX Editor commit eeed873.
Hotkeys implemented in SLX Editor commit 47179cc.