I did some rebalancing recently, and couldn't find it. You can sort by capital gain per lot, which isn't very helpful if your lots are vastly different sizes. Thankfully I don't have that many lots, and had plenty of capital loss carryover to offset the gains, so it doesn't matter that much, but it's annoying, and it's probably the straw that's going to get me to actually move to a better brokerage. (which I guess is fine for Vanguard, if I'm at a different brokerage, it reduces Vanguard's costs)