How To Fix UAS138 - Key field &1 must be displayed

SAP Error Message - Details

• Message type: E = Error

• Message class: UAS -

• Message number: 138

• Message text: Key field &1 must be displayed

What causes this issue?

For creation and processing of the object, key fields must not be
initial. The configuration tool prevents you from closing the window
because you have declared a key field as 'Invisible' without filling the
field by means of a formula. Therefore, the key field would always be
'initial'.

How to fix this error?

Assign a value to the key field declared as <LS>Invisible</> using a
formula at the time of creation (intialise or complete).

Error message extract from SAP system. Copyright SAP SE.