Characteristic "&" not yet created

What causes this issue?

The characteristic you want to refer to has not yet been created.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Choose a characteristic that has already been created, or create a new
characteristic.
IF &DEVICE& = 'SCREEN'
<DS:TRAN.CT01>Proceed</>
ENDIF

Error message extract from SAP system. Copyright SAP SE.