To manage returns of your products made to the consignment store, you can raise a credit note directly from the invoice of that sold unit, and identify the quantities to return to your consignment store's inventory.
On the Products Tab, you can dictate the quantities the consignment store will be credited for (the unit/s returned):
Once the quantities are returned and received, click 'Back to Stock' - Click [Save]
Here you can enter in the quantities to send back to your CONSIGNMENT stock as this stock has been returned to the consignment store and held by them.
This will not create an adjustment within your product stock inventory as with when you send units back to stock within a return authorisation ; as this stock will remain within your consignment customers possession.