Simple: selecting all tracks in mixer

I might be missing something really obvious, but…

How do I select multiple/all tracks in the mixer?

For instance, if my levels are getting too high and I want to turn all tracks down by the same amount to maintain the balance.

natively not possible, but through a tool;

If you just want to adjust the volume of all tracks, use the pre-mixer in the master track. If you want specific tracks and you find that you’re adjusting the same ones a lot, it would be useful to create a group.