If I paint select a few cards, it generally works if I then shift-click on another card. It usually gets added to the selection. But shift-clicking on a selected card does not deselect the card. Also, sometimes when attempting to shift-click, I get put into edit mode of the card I clicked on, and my entire selection goes away.
ah, so playing around with it more…shift-painting works a lot better. but when I try to be precise and just shift-click, it mostly doesn’t work. maybe I shouldn’t expect it to work since normally you select only by painting. but that was my expectation, and sometimes it sorta works.