Chart (modified in place).
Line index.
Event layer index (0 = first layer).
Fractional beat where the event starts.
Fractional beat where the event ends.
Line X at startBeat (chart space, ±675 is half-screen).
Line X at endBeat.
RPE easing type 1–28 (default: 1 = linear).
Add a moveX event to a specific event layer of a line.
If the target layer index does not exist, intermediate layers are created automatically.