The Next Task Action will trigger another task. If the triggered task is already running, it will not be started again. The configuration dialog of the action offers the following option:
Follow-up task: list of tasks the current user has access to
Note: the execution of Actions is performed without any particular order, so other actions may be executed after the follow-up task has been triggered. If a Next Task action is defined multiple times with the same follow-up task, it will still only be executed once.
Note: there is a mechanism to avoid an endlessly executing loop of tasks, that is: if the same task has been executed before, it will stop the execution. Loops should be avoided during the task configuration.