I experimented a bit with that for my prototype Lil' Crane and I didn't find a satisfying solution. Box2d lite is well suited for the Playdate because it is limited in scope which also mean that it is a bit limited to do stuff like strings.
In the end I ended up using a single joint for a whole rope and just render the rope with a curve if the distance between bodies was less than the length of the joint.
If you want the rope or chain to actually collide with the other bodies, you need to create a series of slim bodies and link them with show joints. But the issue is that is will not be great for performance and I think bodies will very easily get crazy and unstable. I could work but it will need a lot of tweaking.