Is it possible, for example, when the 'H' key on computer keyboard is pressed to send "Hold Pedal ON" MIDI message to MIDI track? And when 'H' key is pressed again to send "Hold Pedal OFF" MIDI message to MIDI track.
You can map a key to midi notes with the method Joel Corriveau mentioned, and then send that out to a midi track having monitor or record arm set to on, outputting it to a virtual midi channel. Then you can use http://www.bome.com/products/miditranslator to convert the note on-off into pedal or something else.
Complicated, but it should work.
Not sure if this helps, have you tried hitting the "Key" button in the top right of the screen?
Once you hit "Key," then click on whatever parameter, or on/off switch on a plugin, and then press the keystroke you want it mapped to. Then turn Key mapping off.
Look in the manual for "MIDI and Computer Keyboard Remote Control."
Does that help?