BCO Extension Field - Not visible in Code List Restriction (Administration)

Hi experts,

we have created two extension fields on opportunity. For both fields we have created corresponding BCOs as displayed below.

Now i want to filter the fields via the Code List Restriction Function (WC Administrator):

But my fields are not available in the maintenance dialog:

Standard fields as "Sales Cycle" or "Source" which are also realized via BCO are available. And if i use static code lists for the fields they are available in the Code List Restriction, too.

How can i filter Extension Fields with BCO as datatyp in the Code List Restriction? In my scenario i will not be able to filter the values via context mapping or coding, because the two fields should be available in the SAP Standard Modification List Structure for Products in the Opportunity.

I'm grateful for any answer.

Thanks and regards,

Steffen