Yes, pitch bend is possible in the Vita MIDI Editor even if you're not using a MIDI keyboard controller.  I have just submitted a tutorial on this subject.

http://www.magix.info/us/creating-pitch-bend-in-vita-midi-editor.online-training.619827.html

As the tutorial states, the Vita Instruments and Revolta synth voices are only capable of a pitch bend of +/- one whole note/tone.  So, that is the case for the Vita "Power Chords", which is still enough to give your MIDI guitar a more realistic sound although nothing extreme.