While creating a new workflow, you can use the custom action output as an input for the next action in the workflow. In this case, the output in json could be passed as an input for the next action using 'Dynamic mapping' that will become visible in the workflow once the custom action is added in the workflow. 

So, first of all please create and submit a custom action* that will have json as output. In the example below, the custom action to generate the random password was created and returns the result in json.  

Then, once the custom action has been added in the workflow, you can add the next action and will see the dynamic mapping option that allows you to map the output in json from the previous custom action as an input for the next action: 

 After clicking on 'Add Dynamic Mapping', select the custom action from which the output should be taken, add display name and the path response[0].output. Please note that the output should contain exactly the same as what is included in the custom action with the uppercase and lowercase.


* For more information on how to create a new custom action, please refer to the article on how to manage custom actions