The wing man still gets 5% of trade profit in 2.3. The profit is not shared but paid to the wing man in addition to the profit.
But you may find it painful to do this due to this bug https://forums.frontier.co.uk/showthread.php/344452-Ship-Constantly-Drifting-In-Station-When-In-Wing-Docking-Near-Impossible?highlight=drift
I would like to know if others get this bug as it has made Wings unplayable for us since release 2.2; this was reported by a least half a dozen players on bug reports now deleted. I would have thought more players would have complained about this if everyone had the same problem though.