So, just to make sure I understand. You want to have a web application that shows a map, and when using it in Argon4, you want to have an AR mode that a marker on the screen.
When you say “layer marker”, I assume you mean some sort of content floating in space at that point?
Have you looked at the argon-aframe samples? The geolocation sample puts markers at points in space in the world: they could be near or far.
DOMParser or some external package like
geoxml3 (https://github.com/geocodezip/geoxml3). Then, iterate through that object, looking for Placemarks, which should have a geolocation (longitude, latitude, perhaps altitude as well if you supplied it). You can use that geolocation to create
Cesium.Entity objects that you can use with
argon.js (as the geolocation demo shows).