Official comment
If you want those newly-added tracks at the top, select the "track number" column, and reverse-sort it by clicking it a second time.
Because playlists are ordered in a "numbered" fashion, this allows you to put songs in a specific order, so newest ones are ALWAYS added last. If you want to move them, you can sort by numbered order and drag-and-drop them to the desired position.
If you want to have the newest ones at the top, AND first, reverse sort, then click PLAYLIST on the menu, and select Renumber Track Order.