No that is not possible.

I assume your question is about applying Portamento Time, is that correct?
Portamento has a couple of CONTROL CHANGE numbers already. I doubt very much that the MIDI specification is going to change (but who knows). Aftertouch is a control that is not generated by your MOX and is a message category all its own in MIDI. Velocity has no place in this CONTROL SET area, it is applied directly as a source to the OSCILLATOR in the Pitch Sensitivity area of the Oscillator; it is assignable to the FILTER in the Filter Sensitivity area, and of course to the AMPLIFIER. It is not that is isn't available as a Control Source, it simply has its own parameters within the target destination. (since this engine is targeting musical instrument emulation, the focus of some the assignment choices always seems to lend themselves toward that goal, primarily.)

You have CONTROL CHANGE 5 = Portamento Time
You have CONTROL CHANGE 65 = Portamento Switch
You have CONTROL CHANGE 85 = Portamento Control

You can set a variable Time amount as a DESTINATION to any continuous controller (say you set it in a CONTROL SET so MW(01) is set to "Portamento Time"). Then you can assign the activation/deactivation to an assignable FOOT SWITCH set to cc65 (set in UTILITY). The FOOT SWITCH works like a momentary, when engaged your have Portamento, when disengaged you do not. Or you can opt for FULLTIME or FINGERED as your setting within the Portamento setup
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The position of the MW (or your selected control) will determine the length of time it takes for the note to reach its final resting place, and either the Foot Switch or your playing gesture on the keys will turn it ON and OFF. Make sense?

Using the controls and controllers already available probably is your best bet.

Thanks Phill, your assumption is correct I'm mainly talking about controlling Portamento Time by using Velocity as the input source. It's refreshing to read your posts and review everything again. My point was if it's possible to provide this option in the menu. Using MOD wheel is not easy for live performances.

Using MOD wheel is not easy for live performances.

Oh, it is too. 🙂 Almost everyone can easily use MW, Yes, it does take some practice. You would find using Aftertouch and/or Velocity absolutely impossible for setting Portamento Time. How do you envision that would even work.

Perhaps you can explain why you find the MW difficult to use. You can select any controller (AS1/2, FC are available).

Thanks for asking Phill. Some of au-plugins I have for Mainstage can play legato based on how soft or hard I hit the keys. Also I guess, on MOTIF, the after-touch option can do the same task, but on MOX our closest option could be velocity if I'm not mistaken.

Here how it works in the VST I used:
If I hit the 2nd key with a high velocity, the portamento time is short while if I hit the 2nd key soft the portamento time is long. I can't be that precise with MW and turning MW to min and max for every key played is almost impossible.

I'm not sure if I'm using my MOX correctly or if I'm taking advantage of all its power to create a nice sounding string with legato, but so far it doesn't sound like something I'd use it for a solo performance.

Here is the type of string I'm looking for (David Bitan from Israel): String Example

I know how to create a similar sounding VOICE (timing, detuning etc of elements), but what I can't achieve with MOX is a comparable legato/portamento...

Seriously, that does not sound like it was done with either Velocity or Portamento and it certainly was not done with Aftertouch. I do believe you can accomplish this type of sound by selecting the right library of instruments for your MOX - I will research it and get back to you.

I'm still waiting for an expert advice about this matter.