If you set the outputs of tracks to AUX tracks, do the Export Tracks and only choose the AUX tracks for exporting, you get silence. Any tricks to overcome this without having to set a number of busses (one to each AUX track)?

What are your Aux Tracks output set to ?

My master buss.

If I set a dedicated buss for each AUX track and do the "Export Bus" it'll go fine, but that should be unnecessary IMHO.
It would just be faster if you could do the "Export Track" --- and it would save you from naming the busses/files, too.

Try setting your Aux Track to the same output that your Master Buss is set to (which should be your interface outputs) instead of sending to Master Buss , also mute Master Buss when exporting Aux Track.

No change. All silent.

Can you post screenshot?

Try Ctrl+Shift+A and then export. Sonar has a nasty habit of "sticking" to the last selected track, if there is one, regardless of what you select in the Export dialogue.
 
For example, if I select a track or Lane, then export Entire Mix, many times I only get an export of the previously selected track, not Entire Mix.

An Aux track only has signal during real-time playback. You'll either need to record it first, or export with Fast Bounce disabled.

brundlefly
An Aux track only has signal during real-time playback. You'll either need to record it first, or export with Fast Bounce disabled.

This is likely the answer. I would also imagine that the tracks feeding it would need to be audible during bounce. I do not know how Sonar would handle that during a Track Export process. Like if you select only the Aux track then perhaps that is all that is "audible" to Sonar during the export.
 
In that case, if what Brundlefly suggests doesn't work, then Select all the tracks feeding the Aux track as well (in Sonar and in the Export dialog). Then delete the extra tracks once it's done.
 
I do think Brundle is probably right though and that should not be necessary (if the Bakers thought that far ahead).
 
BUT as Brundle ALSO said you can simply Arm the Aux track for recording and hit record and the Aux track will create a clip of exactly what you want. Then you can just go into your audio folder and get at the file OR drag into into the Broswer (to a desired file location) OR do a proper Export. Unfortunately the last two create a new file while yankign it directly from the audio folder would be the exact file in the project Aux track... so perhaps hard to find unless you name it something that will stand out. I like to name things with AAA at the start if I need to find them quickly in large folders.
 
Just some thoughts.
 
Cheers.