Yes, you may mark down a Vendio Store item by first selecting the item to edit. Then scroll down to the Store Info section and click the gear (circle shaped) icon to the right. Then check the box for "Sale Price & Dates". This will turn on the sale fields below, and you may enter the sale details there.
You may also do this for multiple items in bulk under "Items" --> "My Items". Then use the "Find & Replace" button to find the items that you want to put on sale (there is a percentage option in the replace field).
