We already have a mass assignment for Sites but customers may change which vendor they purchase their items from often depending on the price at the time. It might be 100+ items that the user is now going to be purchasing from a different vendor and as of now unless you use eConnect or and integration, you would have to do it 1 by 1 for each vendor to assign them to the items which can take hours.
Under Review
Ideas Administrator

Thank you for your suggestion. We will consider this functionality for a future release.  

Best regards. 

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