According to the feature announcement, I should be able to enter a comment or code suggestion that applies to multiple lines of a PR by dragging the blue plus icon down. A blue line appears showing the extent of the selection.
But when I do that, I don’t get a blue line, I get a second plus sign that moves with my mouse pointer. Any comment I create applies only to a single line of code, which means I can’t suggest edits to multiple lines of code.
This post suggests I can alternately select a block of lines by clicking one line number and shift-clicking a second. But that doesn’t work either; shift-clicking a second line simply deselects the first.