Selecting via Click & Drag

Kukurykus: Yeah, I realize this would be so much easier to demonstrate visually than describe with words. Second paragraph was just an example of what I meant, where I end up with many "paired" images, whether they're a large set of screen grabs from two monitors, or both color and B&W versions of the same shots. In the grid layout, those two images land side-by-side in the viewing panel. I may want to delete or move half of those shots (all the B&Ws, e.g.). If I have 50 images (5 rows of 10 images), and every other one is B&W, I used to be able to put my cursor at the bottom of the screen, and – while holding down the alt/command key – click and drag up EVERY OTHER COLUMN. (See attached images) That was a quick way to select half the shots I wanted (25 in this case) to move, delete, label, etc., in the next step. Now, I can only select one column that way, and I then must click on every other desired shot individually, which can be rather tedious.