Not directly, but there is a work-around. Create a Group Channel track. Now, route the output of the Instrument track to this Group Channel track. Next, create an Audio track. You then select the Group Channel track as the input of this Audio track. Now, you can record your Instrument track as an ordinary Audio track.
Yes, it’s is a bit complicated, but until Steinberg allows us to route Instrument tracks to Audio tracks, this is how you do it. Mind you, you loose the conveniences of “Freezing” the track. (see below)
On the contrary, my dear mroekalea. You can easily unfreeze the Instrument track, and continue editing the MIDI.
The benefit over exporting is that you don’t have to re-import the audio file and remember to mute the Instrument track. Cubase takes care of all this for you, by the click of a button. If you then find that you need to change a note, just click the “Freeze” button (now called unfreeze) again, edit your MIDI and hit “Freeze” again. Much faster and more convenient than “messing about” with manual exporting/importing.