How to use macros?

[pH142857]

My new mouse doesn't have horizontal scrolling on its wheel, so I'm trying to emulate these events with the mouse side buttons. I'm starting by getting the grip of how to use macros. In the examples, I can see the wheel(down, 10) and wheel(up, 10) events but I can't make them work.

Reproduction steps:

• in Input, I add a side button
• in Output : type = Key or Macro; target = mouse; data entered: wheel(down,1)
• I press Apply
• I press said side button while I'm in a browser page

Expectation: the page scrolls down
Reality: nothing happens.

NB: I first tried to map the button to a keyboard key just for testing, and this works fine.