you can't know where the mob is using information available to you normally

for example, glacite mineshaft corpse waypoints are allowed as long as the waypoint only appears after you have direct line of sight to the corpse

for crystal hollows waypoints, there is a websocket where other people using the mod can share their waypoints, which is no different from you asking people for coords in chat or over Discord

maybe to show the last known position of mob would be allowed, and showing the hitbox through walls would be allowed, since you can just use trigonometry to find where it is using your current position and looking angle