PokerTracker

Where are the columns underlying the Board Texture quick filters? I want to add some custom stats to reports that make it easy to see when a flush draw completes, or a straight draw gets there, or the board pairs etc.

Are there already any custom stats floating around that do this?

There are no existing columns for board texture. If you want to build custom statistics of this nature the easiest thing to do is create a built-in filter for the texture you want and then extract the information you need from the PokerTracker 4 log file - see this post.