Yes! Inside the shattered wilds save folder there's a worlds folder where you can either copy your world to share with others or place a world someone's given you. I know one of the people who helped with art on the game shared her world in the playdate squad discord server.
In terms of challenge maps, you could even conceivably create a world in creative mode and then change the world type in the save data before sharing it to make an adventure map, for example.