Vendors can apply for a refund for specific order from their order tabs here: WCFM Vendor Dashboard -> Orders -> Order Item list.
Upon clicking on the refund icon ( placed under the actions column) the vendor will be prompted to fill in the details of the claim like this:
While the Product name is pre-filled in the above pop-up shown, the vendor has to fill in remaining details for claiming the refund such as:
Refund Request : Here the vendor can select is he/she will apply for a full refund or partial refund from the drop-down. Incase of partial refund, the vendor has to fill in the refund amount which is to be claimed.
Refund request reason: Here the vendor can provide specific reason for claiming a refund against an order.
Once the request has been placed and approved by admin ( either automatically or manually), the refund gets reflected in the order list as shown here ( for partial refund):
Note that if the vendor had already requested or withdrew commission before, then they will not be able to ask for a refund.