The set property action sets the value of a selected model's property, either based on another property or a specific value.
You can set a property value on the source model or any model related to the source model. If the related model is one-to-many, this sets the property on all instances that apply.
For example, in a leave request workflow, after triggering the workflow but before approvals, you can set the Status property to In workflow and the icon color property to orange to illustrate pending.
In this screenshot, we have a set property value creating a value out of page IDs: