How to add tooltips to waypoint markers

Is there any way to add additional information that can be viewed when the user hovers their mouse above the waypoint markers?

alternatively, is there a way to add custom markers by themselves to a map that has a route rendered on it?

This is unrelated to GraphHopper. If you are developing this for the browser you’ll have to use a toolkit like leaflet, openlayers or maplibre and read up on how to do that. (the code depends on the toolkit)

Or are you asking this for the JS client demo?