Martin Winkler - 2009-06-27

I was looking for the same feature, so I just downloaded the source (although I don't really know C that much), and found this comment in main.c:
// * if there's a notification area AND there are one or more 'autostart' tunnels
// then maindialog is hidden (ie 'start minimized to tray')

So I did what was obvious: set one of my tunnels to autostart, and gstm is working as expected.