Behemoth Drivetrain used to make an electric to manual shift kit but don't see it listed any more
EDIT: found it here:
https://behemothdrivetrain.com/product/electric-to-manual-shift-kit
They were about $450 last time I looked, a bit pricey now, but looks well built
You do need detents to hold shift rod in place if you install your own adapter
The shift motor has a contact wheel that turns when motor turns, this is how the "Control" knows what position transfer case is in at all times, at key on it see what contacts are open and closed so it "knows"
And that how the Green light worked, when contacts were correct for Neutral the Green light came on, same as 4high or 4low lights on dash
If you wanted you could high jack motor wires to disable "Controller" from moving the motor, and allowing you to move it
I think the "controller" sends out 5v or 12v on the Yellow/white wire, pin 8
Then it watches which of the other 4 wires is sending back that voltage(closed contact) or not sending it back(Open contact)
Looks like you could use Pin 7 Orange/white wire
Add LED to that wire, so it would be OFF in 2WD but be on in 4H, then it you manually move shift motor counter clockwise, when LED goes off, STOP, you would be in Neutral
If you get lost just return control to the system and turn key on, it would move back to 4High or 2WD which ever position the dash switch was in