Here's a home made soft shackle. It's length of dyneema with a small loop at each end, a tab of webbing that serves the purpose of the knot but is more positive, and piece of ribbon to make it easier to undo.
The BRM parawing uses a simplified form to hold the lines on the bar. It's got the two loops at each and a pointed bit of webbing in one of the loops.
You just loop it through the leash loop on the wing, pass it round (in the form of a reef knot), then close it and pull it all snug.
The leash loop being snug against it makes doubly sure the soft shackle can never accidentally open. You could make the soft shackle as simple as you like. A length of dyneema with a loop at one end and a knot or webbing tab at the other. It's forming a reef knot shape with the loop on the wing and the soft shackle that makes it ultra secure.
If you want to be super simple, just have a big loop on the wing, or on the end of the leash. Just pass the whole leash through the loop and it'll never come apart. It's a tiny bit fiddly with coiled leashes. You just have to hold the coils together while passing the leash through the loop.
I've standardised on a larger spliced loop on the wing, and a velcro leash swivel attachment. I've got dozens of those from all the leashes I've owned over the years.
