This site is being deprecated.
Please see the official X‑Plane Support page for help.
You might try this. Place your mouse over the knob until the 2 curved arrows appear. Now push and hold the left mouse button. Slide the mouse straight left or right and you may see the change for which you are looking. But, this is just a guess as I do not have the add-on CRJ-200.
This site is no longer being actively maintained.