Set Workflow Variable is a fundamental workflow action that allows you to assign a value to a variable, based on the current place and decisions made in the workflow process. You could always create multiple variables within the action, but up till now you could only set one variable at a time.
This approach meant that every time you wanted to set a variable value, you would need an individual instance of the Set Workflow Variable action. For instance, if a workflow had 2 variables (discount price and sales value) that were set in 2 different process stages(proposal and negotiation), you would have had to use 4 instances of this action. This also meant you required a lot of canvas space in the workflow designer.
You may have noticed all the past tense in this discussion. That’s because new enhancements of the Set Workflow Variable action now allow you to assign values to up to 20 variables. Revisiting the earlier scenario, if the workflow designer needs to set 2 variables progressively at 2 different stages of a workflow, you now only need 2 instances of this action.
The interface has been updated with a clear “Add Variable” button on the bottom of the left-hand side and a delete “X” button per variable.
The enhancement is available to all new and existing instances of the action. Previously configured Set Workflow Variable action instances will contain the current variable in the first position already set to its historical value. You can add new variables to this instance.
This change has come at a great time with Nintex introducing subscription pricing and is a proactive response to help you reduce the number of actions required to manage variables in a workflow. Fewer actions translates to lower costs incurred by you and helps optimize the designer space required.
Nintex for Office 365 help: Set Workflow Variable action