No, the whole point is that it does not need to be an actual waypoint. I guess the reason it doesn’t show up is that you are just entering one GPS point. You have to enter at least two. Maybe in the search bar of FPL in your infinite flight write down the name of an airport and then a space and then the coordinates above. For example:
Now it should show up at the other end of the route.
It does not work like how the search works for actual waypoints. For waypoints, when you search and find their name by clicking, the map moves and zooms to where that waypoint is, but this is not the case for GPS coordinates when entered in IF. Instead, you can pick a well known airport or whatever other waypoints somewhere to lead you where the GPS coordinate of your interest is standing (still there won’t be a real mark for it on the map).