Honestly I use the Valheim World Generator(https://valheim-map.world/) to show me the different locations of the Trader, Only because once you have gotten within a certain distance to the Trader, He pops up on your map and thats the only one you can use. Trader is a one time find but there are different Trader spawn points. Once you've set it to show on map, the other options of spawn points are taken away.
Hope this helps