Can anybody tell me how to assign after touch to the mod wheel please? If possible.

Sorry, that’s not possible. MOD WHEEL is a physical controller that always generates a specific message cc001 Modulation Wheel. cc001 (Control Change) can be applied to most any function, it does not have a fixed function. It is most often used to apply Modulation depth to pitch (vibrato) but that must be assigned to the wheel on a per program basis. AFTERTOUCH (Channel) is also a physical controller that does not generate a cc message. Aftertouch, like Pitch Bend, and Program Change, has its own dedicated category of message.

Commonly used MIDI messages
Note-On messages are represented as “9n”
Key Aftertouch messages are represented as “An”
Control Change messages are represented as “Bn”
Program Change messages are represented as “Cn”
Channel Aftertouch messages are represented as “Dn”
Pitch Bend messages are represented as”En”, where “n” is the MIDI channel, 0-F.
System wide messages are represented as “F”

The MODX is not able to generate either kind of Aftertouch message (Key, nor Channel). The Ribbon controller, like the MW, FC, Sus, Sliders, Assign Knobs, Assign Switches can send cc (Control Change) messages.

Anything useful would be appreciated.

You must find alternate controllers to function in place of the Ribbon and Aftertouch, because the MODX physically does not have these physical controllers. While physical controllers typically only differ in “how” they are applied... the only difference between Aftertouch sending values from 0-127 and the MW sending values from 0-127 or a Foot Controller sending 0-127 is the “how” in how it is applied.

Aftertouch allows the player to apply 0-127 by varying downward pressure on a key... this can be used in a very intuitive way to add Modulation. The Ribbon allows programmable variance — it can be minimum to maximum or it can be used to increase and decrease values around a centerpoint... this can be used in a very intuitive way to apply Modulation (great for real vibrato when a Tune parameter is assigned). Aftertouch can only be applied during Note-On and will always reset to 0, the Ribbon can set to ‘Hold’ the last value or ‘Reset’ to center when you disengage.

There is no direct substitute for the tactile feel of these control devices, sorry... (short of using an external device via MIDI), but you have new ways to approach applying change (modulation) To sounds like guitars, synths, etc. Learning to program multiple functions to the MODX Super Knob System can be a viable alternative, learning to use the XA CONTROL to manipulate articulations is another alternative.

... adding - for reset type controllers that MODX does not have (ribbon in reset mode or aftertouch) - the closest controller to achieve this reset capability would be the assignable switches in momentary mode. They do "snap back" to a reset number. The downside is that they are only "on" and "off" - not varying degrees of "on" like ribbon and aftertouch. However, there may be a reasonable "on" value that will be usable where you can reassign a "Mod/Control" -> "Control Assign" source of RB (reset) or Aftertouch to an A.SW (1 or 2).

The suggested superknob does not automatically "snap back" to a reset position - but there are two buttons for storing the superknob position. Either one could be use to program a reset position so you would spin superknob as the "fake ribbon movement" or "fake aftertouch pressure" and then press the "position" button to reset back to the resting value. This can be managed.

Even better - if you can lose the pitch bend (force it to +0 / -0 note range) - then Pitch Bend is probably the "best" controller to swap out aftertouch or ribbon (reset) in "Mod/Control" -> "Control Assign". Pitch bend automatically snaps back to a resting position when you let go. For aftertouch - you'll just need to adjust the curve since the snap-back point is not 0 - but 64. Bipolar can be used assuming for aftertouch you only use positive movement of PB (this will start at 0).

None of this will send aftertouch (or ribbon) out of MODX. This is all about if aftertouch (or ribbon) is assigned to a parameter through the assignment matrix - you can swap aftertouch/ribbon out as a source with these other suggested controllers.

Many thanks. I did have my doubts about the use of these functions.