How can a supplier add attachment to an incomplete purchase agreement using 'Transfer to Supplier'

Summary: Supplier is unable to add attachment to an incomplete agreement or as a change order to an approved agreement from Supplier Portal.

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There is a business requirement where Supplier needs to update an incomplete blanket purchase agreement. Oracle provides functionality of 'Transfer to Supplier' for incomplete agreements, this is enabling Supplier to update the agreement using Supplier Portal but there is no option to add attachments. How can we enable Supplier to add attachment to draft or open agreements using supplier portal?

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