Flow logic: Data element supplement &1 does not exist in dictionary

What causes this issue?

In the event
PROCESS ON HELP-REQUEST
the flow logic contains a statement for the self-defined F1 help
FIELD <fieldname> WITH <number>.
The number of a data element supplement specified in <number> for the
data element referenced by <fieldname> does not exist.

System Response

If at the runtime of the screen the F1 help for the screen element
<fieldname> is requested, the system attempts to display the data
element supplement documentation in addition to the data element
documentation.
If the supplement documentation <number> is not found, only the
standard documentation is displayed.

How to fix this error?

Verify if the data element supplement specified is correct.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.