As a Studio user on the workflow graph, I can select a specific type of node called "Sub workflow". I can edit it and, beside usual automation chains configuration etc … I can set the workflow model ID that should be called (ideally with an autosuggest that still enables to put a new value), and edit the values I can pass to workflowVariables of the sub workflow.
From the graph, I can with a single click reach the sub-workflow graph (in the same browser window)