Expression Dialog

Low priority, but also easy implementation, I was recently addressing a question on the Reddit forum of someone getting sideways lightning with one of the brushes when using the pen, and downwards with the mouse. I tracked the problem down to that his XP Pen did not do Bearing, and instead reported a consistent value of 90 or so, rather than the mouse value of 0, so he just had to change that expression and set the angle manually. It made me realize that there's no one-stop place to see what parts of the brush are dynamic and what they base it off of, as all of those settings are in different dialogs.