How can I auto-populate a dynamic drop down menu with store vendors?

[theflowerpot]

is there a simple way to have an auto-populated menu of your store vendors? 

IE Brands as the top level item and the vendors automatically list as a drop down upon hover? 

looking for a way to automate as new products are added to the store versus manually add 

IE https://theflowerpot.co/collections/vendors?q=Tetra