Does MapNav 2 have functionality to hightlight cells, for example, highlight the cell which your mouse pointer is over? Or to highlight a path? or to highlight the cells to which a selected unit can move to?
You should check the API but you could always do this with a raycast.
Presentation is up to you. “Showing” a cell or path could be achieved via projectors or simple textured planes.
Have a look at any of the sample scripts to see how I ask MapNav what cell the mouse is over when clicking in grid area. Same can be done at any time, not just when clicking with mouse. You might want to at least check if mouse pos changed before making this query though to safe on some unnecessary compute.