Select an operand

What causes this issue?

Position the cursor on an operand for an active schema step.
If you select an input operand, all preceding schema steps are
displayed which update in the indicated step.
If you select an output operand, all following schema steps are
displayed in which the indicated step updates.
Note that there are variants with output operands that are excluded
from the update.
You can recognize these fields by doubleclicking on the relevant
variant in the schema. You find the field <LS>Update type</> on the
following screen. Entries in this field are output operands of an
update character.

System Response

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.