Description of what you are sharing
This allows you to do a trackpad three finger click to perform a middle-mouse-down click. It will keep the middle mouse button pressed as long as you are still touching the trackpad with at least one finger. This allows you to move the cursor and thereby simulate a real middle-mouse click as needed for e.g. CAD programs like Archicad.
NOTE: This requires BTT 2.506 alpha or later to be imported correctly
Copy & paste this JSON snippet into BTT, it will add a Trackpad 3 Finger click (responsible for the middle-mouse-down cllick and a named trigger (responsible for the middle-mouse-up) in the "Other" tab in BTT:
The example is available here: