No such feature in STP, much to my dismay.
If you want to do it across a large file you'll need something like Pro Tools, or Logic Pro and then export all the seperate regions. Note that Pro Tools LE can be purchased quite cheaply with their Micro hardware.
If you're just removing silence from the start and end of a file the only thing I can think of is the Auto Trim/Crop tool in Sound Forge, files can be batched too. That's only for Windows though unfortunately.