Thanks @Con-Hennekens, I was able to import my POI/waypoint file in using this method.
The POI's are not listed in the POI tab, rather just the name of the imported file in the library which contains a quite a few POI's which can't be selected to view.
The POI's show on the map only when the maps is quite zoomed in, so you kind of have to know where they are. But I can use these to create a waypoint, so all is not lost.