Inspired by moet's https://wago.io/p99rsw1p_ but adjusted to be more world marker oriented, along with some extra options.
We primarily went with using four world markers to indicate the arrows, going clockwise from star, circle, diamond then triangle markers. Place them like in the attached image, align using the map facing north.
If you enable the play sound option you can adjust the sound played under Condition 1 from the default Air Horn to something that suits you better.
Recently the logic how assignments were made changed, which means you should use the same latest version so that everyone is properly assigned the same way, otherwise you'll end up having some people assigned to arrows when they aren't needed. The new logic will prioritize to place melees on the right/orange clump of arrows, and ranged on the left/star for consistency, and also consider stacks of Woe.