Can we change tracks within a song or pattern?

You can change Tracks by touching the front panel buttons 1-16. Since this changes the transmit channel of the Keyboard, there is no Channel message to switch Tracks. Just touch the button [1] thru [16] to transmit on that channel.

The Foot Switch (FC3/FC4/FC5) and the Foot Controller (FC7) do not address the MOXF with MIDI commands, they address the MOXF directly. If, for example, you set the Foot Controller that is plugged into the FOOT CONTROLLER jack, to send cc74... it will dutifull Send that Out via MIDI, but it does not address the MOXF via MIDI.

If you want the FC7 to do Filter Cutoff (Brightness) you would Assign the FC1 = cc4 Foot Control
Normally FC1 is set to Expression cc11
By setting it to cc4 Foot Control, you can decide exactly what it sends... from within the Control Set of that Voice. Then within the Control Set of the Voice you would assign “Cutoff” to that device.
If, for example, you want Control any particular function, those functions will appear as a list under the DESTINATION area of the Control Set.

The MOXF does not address itself with MIDI.
It Outputs MIDI so that you can record it and play it back, but it does not “talk” to itself initially with MIDI commands. This is so it can work without being connected to any external devices. (Besides keyboards predate MIDI).