I am starting to configure BTT (better touch tool) to make some trackpad gestures ... I noticed that if I put my middle finger on the trackpad and then tap to the left or right of it with a second finger, it will switch to the previous (or next) tab in an internet browser. I can NOT for the life of me figure out where that shortcut is located. It's not anything in BTT, since I have not added any gestures yet, and it doesn't seem to be in the trackpad preference either ... Any ideas?!