Linked dockers like gitlab + postgres + redis cannot be updated / initialized / changed any more if network is set to bridge (older unraid versions with probably older docker versions aren't having this problem).
The command /usr/local/emhttp/plugins/dynamix.docker.manager/scripts/docker create --name='gitlab' --net='bridge'... fails with
docker: links are only supported for user-defined networks.
This is related to https://github.com/docker/cli/issues/2030
So there are two ways to fix this:
1.) Use this fix https://github.com/pcellix/cli/commit/246a69a04e94332f93a294b073bb233ef9056f6f
2.) Add another option to the Network dropdown 'Default', which omits the --net='bridge' parameter, which is effectively using bridge as network, but doesn't bail out with an error.
As long as this is not fixed, the only way to update / initialize / change a docker which is using links is to copy and paste the docker command from the GUI, remove the --net='bridge' parameter and execute it in the shell.