F4 list of values not enabled in MDG CR for field "Units of Measure Group"

Hi Experts,

I have a requirement to add "Units of Measure" field (MEGRU) to Sales View of the MDG Change Request/UI (ECC6/Ehp5).

When I am adding the attribute ZZMEGRU and providing the data element MEGRU I am getting error "Data Model MM, entity type ZMVKE, attribute ZZMEGRU: Invalid check table"

So I provided the data element with data type CHAR4 it allowed me to create it and i was able to map it.  The field is also available in MDG CR but the F4 drop down is not enabled.

Please let me know what I am missing here.  I have tried to create a relationship for dependent table TWMEG but still it does not work.

Thanks in advance.

Regards,

Rama