You want to set up Exchange Properties in an integration flow.

In SAP Cloud Integration, Exchange Properties can be created and set using:

Content Modifier → Standard way to configure properties.

Groovy Scripting → Via the SAP CPI Groovy SDK, you can dynamically add or update exchange properties at runtime.

Other options:

Batch scripting, XML scripting, Python scripting → Not supported in SAP CPI.

Thus, besides Content Modifier, you use Groovy SDK scripting.