Not sure about this, haven't used it yet , But can you use the new virtual keyboard and assign a parameter to the mod wheel?
USING THE VIRTUAL KEYBOARD
It’s easy to open
the keyboard: look under the Views menu for Virtual Controller/Keyboard, or
call it up by typing
Alt + Shift + 0.
To use the touch screen’s “virtual mod wheel,” tap a key and
while holding slide up for more modulation, or down for less. The mod wheel value latches to
the last state when you remove your finger from the key.
For the touch keyboard, velocity works in a way similar to piano keys
—
the closer you touch to
the bottom of the key, the higher the velocity. Tapping at the top of the key gives lower
velocity. For the QWERTY keyboard, you
can
set velocity manually.