How to change Docker default folder

In docker there are three basic concepts: (1) image (2) container (3) service configuration and data. Storage of images and containers are managed by docker, storage of configuration and service data is managed by the user during the container creation process.

I may be speaking Chinese so keep studying here https://docs.docker.com/

I never tried personally ,but it may be possible by editing :

/storage/.kodi/userdata/addon_data/service.system.docker/congig/docker.json

This is the line that yiu should try to modify ,by replacing the default path with your external drive:

DOCKER_DAEMON_OPTS="--data-root=/storage/.kodi/userdata/addon_data/service.system.docker/docker"