I know there are marker prefabs but they most of the time or always work incorrectly. VRChat's markers are the only markers that actually work properly.

Check the VRC prefabs made from popular world makers here: https://docs.google.com/spreadsheets/d/e/2PACX-1vTP-eIkYLZh7pDhpO-untxy1zbuoiqdzVP2z5-vg_9ijBW7k8ZC9VP6cVL-ct5yKrySPBPJ6V2ymlWS/pubhtml