Find Variable or Text
There are some other great suggestions for documentation of variables, but I would also like to see a way in the designer to highlight actions that use a variable. I envision a Search button in the ribbon that opens a search dialog where I could either select a variable from the list of variables in this workflow, or simply type something in a text box. The feature would search the workflow and highlight all the actions that use the variable or contain the text.
The suggestion for finding and removing unused variables (https://nintex.uservoice.com/forums/229405-1-nintex-workflow-for-sharepoint/suggestions/10843149-find-and-remove-unused-variables) identifies the scenario of trying to delete a variable and getting the error message that it is in use. But where? This suggested Search feature would be a way to find that one action that shouldn't be using this variable so that it can be fixed and then the variable is unused and can be deleted.
Drew Johnston commented
Agreed - it's frustrating to try to find where variables are used in your workflow.