The function outputs can be set for touch on, touch off, or momentary, touch and release. That is done on the same page as the Function button is shown.
FX4 in this video.
You will need a relay or intermediate circuit to drive the coupler.
I was able the map the coupler CV to the Function output the coupler was wired to so you heard the clank when the coupler opened but will have to check the map to see what CV number that was.
Pete