So the title tells it all. How is it possible to “record” (or of course I mean save/export/include) the CLICK’S sound on the Audio Mixdown track? Please try to be as specific as possible 
What I do is build one with a sample from the mediabay because it seems that there is no way to actually route the click to an audio track. Another option would be to route the metronome to a vst and that would give you something to bounce in your final mixes.
if you can record the output of your soundcard , do so and record metronome to an audio file.
thats what i do