In ArcGIS Pro you can add several type of layers to polylines such Marker, Stroke and Fill layer. but in AGOL you have only one option for polylines, and there is no way to add other layers like AGP do.
in the image above, green and yelow powerlines show Marker Symbol Layers for each nodes and vertex. Our main goal is represent each node with a marker for every pole in the Feature Class. ¿it is possible to develop in AGOL?
PD: no english speaker here, sorry for limited writing capabilities