Numbers: Can I highlight the row and column of the selected cell?
If I understand your question, Numbers does this by default - note the darkened row and column identifiers in the image below at AK50.



Edit: ah, I see.. okay, I found an inconvenient hack:


Select the Column containing your target cell
Cmd click the cell above (or the Cmd Click the row index of the cell above)
Cmd click the Row containing your target cell
Cmd click to reselect the cell above your target


Like so:







Maybe you could use automator to make this less painful?