How do I select several to-dos at once?

Three ways: (1) Hold Cmd and click each to-do — this adds them one by one, and clicking an already-selected one removes it. (2) Click the first to-do, then hold Shift and click another — everything between the two gets selected as a range. (3) Click on empty space and drag a box (a "marquee") over the rows to lasso them all at once.