dbt_task = DbtShellTask(
  ...
)
with Flow("dbt-flow") as flow:
    dbt_command_string = Parameter('dbt_command_string', default = 'dbt run', required = True)
    dbt_commands = dbt_command_string.split(',')
    for command in dbt_commands:
      dbt_task(
          command=dbt_command,
          ...
      )