Leaderboard

I don't think you are describing the problem accurately. A portal will not resort until you commit records. Not even if you exit the portal to go to a field of the parent record. If you see a shift in the record's position then a commit has occurred, either by the user or possibly by a script trigger. You could probably prevent premature committing by the user by validating the When? field as not empty. My preference would be to bypass the issue by scripting the process of creating (and possibly editing too) a child record in a card window.