Overview:
Up until now, the output of every connector action required its own variable. This is not a bad thing in some instances, but it can cause some confusion in big workflows. With the latest update, connector variables can be reused between actions.
Example:
Your workflow queries a SharePoint Online list. The workflow then updates some items on the list and then queries the list again. Since the first query is no longer required, the variable from the first query’s action can be re-used.
Note:
To re-use a variable, it must be for the same connector, and the output must have the same structure. Please take a look at the video I've included below for more information.
Video:
Help File:
https://help.nintex.com/en-US/nwc/Content/Designer/UseVariablesinWorkflow.htm#Reuse