Recently came over from jitouch since that doesn't work in Mojave anymore! I'd love to see a Two-Fix Middle-Double-Tap. Similar to Tip-Tab Middle (2 Fix) but instead of tapping the middle finger once, you do it twice, and it can detect that you have two other fingers already on the trackpad, instead of having to tap down with the two finger and THEN tapping the middle.
I have a bunch of 3 finger gestures set up for Chrome. so I always have three fingers down on the trackpad. Being able to just lift the middle finger and double tap it to do something (in my case, close tab) is hyper convenient.
Currently I've got the close tab feature set up for 3 Finger double tap, but it's not quite as convenient.