Lightroom: Add rectangular/column mode selection of photos from grid view

If the user holds shift and clicks a range of photos in Grid view, Lightroom will select all the photos sequentially as if each horizontal strip is one segment of a long photo strip.  For example, in a grid of 4x4 photos named A through P, if B is clicked and then O is shift-clicked, all the photos except A and P will be selected.

I would like to use a different currently unused sequence, such as alt-click, to perform a rectangular selection.  For example, if B is clicked and the O is alt-clicked, you will see B,C,F,G,J,K,N,O selected in a vertical 2x4 rectangle with the outside columns unselected.

I take a lot of bracketed exposures and merge them into HDR photos.  Sometimes the brackets don't work out and I would like to grab only one vertical slice out of it, say to get all the 0 EV exposures.  Or I want to grab all the 0 EV and the HDR merged ones, and compare them while discarding all the other brackets.  Rectangular selection would make it trivial to grab or discard what I need, without resorting to complicated filters.