The mechanisms behind Kubernetes ConfigMaps and Docker Swarm Configs are almost the same. At least, from the functional perspective. Both allow us to store some literal texts in the scheduler's internal data store, and both enable us to add them to containers. The syntax is equally simple and straightforward in both cases. Still, there are a few differences.
Docker is good at preventing people from doing silly things (the politically correct version of the word stupid). An example would be an attempt to delete a configuration. It cannot be deleted if there are Docker services that reference the configuration. Only after all the services that reference it are removed, are we allowed to remove the configuration source. Kubernetes, on the other hand, will let us delete a ConfigMap object without even a hint about the consequences...