Try 85 via switch to ground 87 to actuator 30 could be looped to 86 fromUpdate: This is what I have installed to get the T6 Tailgate to work with my T5.1.
I've cut the connections to the external tailgate pressure switch and inserted them in to wire 57, including an internal momentary switch. Couldn't get the factory internal switch to work with my circuit, but this was a simple workaround.
On press of key-fob interior lights activate relay, sending power to both switches. Pressing either switch activates the Tailgate actuator. When lights go out tailgate cannot be opened.
View attachment 181161
Interior lights