The “Compose” action in Power Automate is a data operation tool that allows you to create an arbitrary object from the inputs. This action can be used to build and manipulate JSON (JavaScript Object Notation) objects in your flows.

In the context of JSON, the Compose action can be used to build complex JSON objects. For example, you can create sub-entities using multiple selects, and then use a Compose action to consolidate them into a single JSON object.