DMS adding a document to bill of materials "general item overview"

Hi,

I customized DMS for bill of materials using the following objects:

STKO_DOC BOM Header 258

STPO_DOC BOM item 257

After this I can add attachements to bill of materials header and item but cannot adding to "General item overview" when I execute CS02.

In CS02 "General item overview" I can see the column "Document" but it is not editable.

Thanks

Best regards