Hi!
Currently, the only visual the user has on which column they have selected in the Results window, is the 3 dots for column options (Data Cleanse/Filter/Sort). It would be incredible if Alteryx would add a border around the entire column that is selected (like you currently do when selecting a whole row) & maybe possibly even bold the header of the selected column.
I think you might be changing the background color from light grey to white, but it's so subtle it's hard to tell. Make it pop!