As an Admin you are able to collect an admin fee for every transaction between the merchant and buyer on your online marketplace.
Admin can edit the default commission from Commission page under Settings > General.
You can add category-specific commission fees by referring to this article.
Also, you can read about our Merchant-Level Commission from here.
*As a general guideline, the average admin fee charged by online marketplaces is around 10-12% of the entire transaction value.