You are correct that Quicken has never handled short positions with the Shares Transferred action. I don't know what workarounds you noted, but the only one I could imagine would be to close the short in the old account at cost - no gain/loss - and then recreate the position in the new account. I don't know enough to think that such an approach is 100% adequate. Given the very limited level of comments about this deficiency, I would doubt that this is very high on their punch list.