There's not really a way to adjust the "sensitivity" of the pressure parameter (when it actually begins), but there are a couple of things that can adjust its response.
First, you can adjust the "Gain" of the pressure modline — higher will make it more sensitive, lower will make it less sensitive. Though, this can potentially limit your ability to hit the maximum value (when lowering the gain).
Second, you can always create a custom "Curve" table to make it so the pressure values don't start increasing until you reach a certain point. I've attached a screenshot of an example. In the example the first 15 values are set to 0, so what would normally be the first 15 pressure values will just output 0. It's not until you get to 16 that pressure starts increasing. It's not exactly the same thing as making pressure harder to activate though — the 0 values will still get output (though that's almost like it's not turned on).
- A little sloppy, but not bad for a hand-drawn line.
2, 3, 5, 13, 89, 233, 1597, 28657, 514229, 433494437, 2971215073