Hi,
You have to create new field in Context node of BTADMINH for this and then you can put code in GET and SET method to retrive the field value from taking the BTPartner relationship entity.
In GET method take BTpartner relation and find the value for the partner_fct and display
In SET method you have to do the same when value is provided in the field you have to take BTPartner relation from BTAdminh relation and check for your partner_fct entity from BTPartner collection using, if entity is created for your partner_fct you can set the value for PARTNER_NO otherwise you have to create the entity using create_related_entity and then set the value.
In both details and BTPartner AB same values will be taken .
Regards,
Deepika.