Oh my bad… I’m not sure how I managed to skip that part of the docs. I’ll update the docs today and add some more information.
The setup should be simple, add a grid to the world in the Grid Editor mode, then set the properties so that the cells cover the entire playable area of the world. Then add the Grid Component to an actor and you should be good to go. The Grid Component uses the actors Root Component to find it’s location.
Can you post a screenshot of the world itself, and the test scenario? Query Grid [Sphere] should function in a similar fashion to a Sphere Overlap test.