You can merge Songs in the Project page, but it's one at a time so I hope someone else has a better way. But if no one does, you could open your project and go to Studio One > Keyboard Shortcuts > then search for 'combine' create a shortcut for 'combine with next track' (I used Ctrl+Shift+C). Don't forget to click assign right below the shortcut, I missed it the first time. Than ok. Back to your project... Select All (Ctrl+A) and hit your shortcut key a lot. Annoyingly, with this method you'd have to hit your shortcut key for each track, so over a hundred times. Like I started above, I hope someone else has a better method. Good luck.