Hello,
First, please excuse my english, I am french. There is a very boring work to do to export all tracks from an audacity project to a set of wave files. A feature ‘Export all tracks’ could be add to menu ‘files’ . The tracks wich are not begining at the start of the project could be prefilled with some Null, so all the exported tracks should be synchronised. I’m very found of Audacity, but this feature takes a lot time to be done manually.
Regards,
Pfeuh
Use File > Export Multiple.
Audacity does not respect white space in front of tracks when exporting. If you want to export tracks correctly offset from zero, select each track (not all together) and apply Project > Quick Mix (Tracks > Mix and Render in Audacity Beta) to each track so that the white space is rendered as silence.
@Peter: I’ll record “export multiple should have a way to respect preceding silence” as a Wiki Feature Request.
Gale
Shame on me… It does exactly what I need! Thank you! 
Regards,
Pfeuh