First, you'll want to make sure your groups are displayed in the Edit window. This is sub-titled Edit Groups. If it's not showing, then click the >> button at the very bottom-left of the Edit window to display this.

Click the to highlight it blue. This selects ALL tracks as a single group. This makes operations happen to all tracks.

Choose Shuffle at the top-left of the screen. This makes things slide over when necessary.

Now you can paste audio into any section ofthe session and everything will slide over accordingly.