I once made a contraption out of the top thread-part of a plastic soda bottle and the lid. Cut a slot down the threads, put your drawstring ends through the bottle end and slot, then tighten the cap to hold everything in place. plastic. survives the wash. Then my Dad suggested sewing the drawstring to the shorts at the midpoint with a few stitches. Much better, you don't have to make and remember to use any contraption.

I've had sweatpants with a continuous drawstring, this is the knot I use to tighten them

https://youtube.com/shorts/1I9_Zxypg1s

I tie knots at the ends of my drawstrings to prevent them (mostly) from retracting

You can find drawstring threaders (bodkins?) on amazon pretty cheaply - if you have clothes with drawstrings it's handy to have one of these around the house.

You can get an inexpensive drawstring tool off AliExpress.

In recent years I've needed to use a Wash & Fold service, and I've gone through at least 8 of them with acrimonious disputes and really awful service.

The last one was getting all my clothes clean, but they always folded them in the most haphazard ridiculous way; some garments were deliberately turned inside-out, etc. (It was kind of a racist thing, by the workers who were not of the friendly owner family at the front counter. Happens all the time to me.)

Another annoying thing that they did was that anytime a garment had a drawstring, it would end up extracted or completely pulled into the waistband. The front-counter owner lady even pointed this out, rather gleefully, and "apologized" and handed me the disassembled pair of shorts.

In the meantime, I found that a lacquered chopstick was very useful to route the drawstring back through the waistband, along with a pair of tweezers or needlenose pliers, to fish out the end from deep inside there.

Since then, I've switched to a service that is treating me with respect, and the lady is amazingly good at sorting and folding! Yay!