The Track inspector has a mini pro-channel module near the top (under gain, above the FX bin). "POST" is right in the middle of that, where you expect to see it. The inspector can be visible with both Track View and Console View.
The Console View has this same thing built into every track, in the exact same spot.
Where you will not find this button is within the Pro Channel strip/module itself (don't open Pro Channel to find it).