You absolutely do not need any kind of ABY. The easiest way would be to plug the mission into the first h9 expression Jack, then run a midi cable from The 1st h9 to the 2nd.
But if you’re building the mother of all pedalboards I assume there’s some kind of controller, that probably will have an expression in jack that with then allow you to send expression to any midi capable pedal in the midi the chain, The only thing you have to look out for if you use it that way is that they all want a TRS cable, some do not.
