904 leaking, just sitting ?

Ima thinking that leak in post 9, is closer to the back of the trans, maybe around the Speed-O adapter. Those have an O-ring AND a seal inside where the plastic gear comes thru.
The O-ring almost never leaks
And if the speed-O cable is on tight and in good shape, you might never know if the seal is leaking. But, if the cable is not tight, well then there it is. To change that seal, the adapter sorta has to come out. And more oil will come out, unless you jack the car up high at the back, or high on the Driver's side. You'll figure it out, but put an oil-change pan under it anyway.
That adapter has to go back in, in exactly the same orientation as it comes out, so mark it. and the plastic gear, where it passes thru the seal, has to in fine condition.