Generally, a device has its own channel, that’s OK here for the H90. In my case, I chose 5.

This channel is the identification for this device, among all the devices in a setup.

A device (H90: ch5) should be able to write Midi commands attached to a specific channel, that is the identification of the device that this command is intended to reach (MobileSheets: ch3)

Here, in the H90, it’s not possible to specify the recipient device because no way to write its channel (ch3).

That makes no sense to write a command with the sender channel (here, H90: ch5) as recipient’s channel !

This is a basic subject in Midi.