A sharpie is a huge help for me. Essentially you set the sling up as is for length to use as a hasty sling. The rear clip comes off and can be opened up into a loop, which goes above the bicep, for a really rock solid prone/seated shooting position, which will require re-adjustment of the front quick-adjust. I put a sharpie line on the inside of the sling with a P written by it for prone and another with H for hasty, so it's easy to get the sling back into the proper length for the different uses.
https://artoftherifle.com/the-loop-s...oop-sling.html