Alternating outputs on same input?

[Qaus-Sphene]

I'm trying to figure out how to macro-script my way into having a single input that alternates between two outputs.
To be more precise, I want mouse wheel down to alternate between the 1 and 2 keys, and mouse wheel up to alternate between the 3 and 4 keys.

Any idea on how to achieve this?

[agammann]

Yes. Give the wheel-down and wheel-up mappings separate state variables. For the wheel-down mapping's Output field:

if_eq($down_next, 1, key(KEY_2).set(down_next, 0), key(KEY_1).set(down_next, 1))

For wheel-up:

if_eq($up_next, 1, key(KEY_4).set(up_next, 0), key(KEY_3).set(up_next, 1))

An unset variable starts as None, so the first event follows the second branch (1 for down, 3 for up). Each branch then stores which key to emit on the next wheel event. The two directions alternate independently. These variables are shared by macro execution, so choose names not used by any other preset. The sequence resets when the variable store is restarted.

The macro guide documents these functions.