Thanks, you are right about asking the Webkul Devs.
Here their answer, seems to be a good timing
"Thank you for showing interest in our module.
So do you want to allow sellers to create booking and reservation products ?
Well if so currently we do not have a module for booking and reservation for marketplace, however we do have one for Prestashop, Prestashop Reservation And Booking Module
You can check the flow of the module from the link.
Now as far as reservation and booking for marketplace module is concerned, it is already in development and is at its fishing stages. Hopefully we will release it by the end of next week if all goes well.
So if you could wait for sometime you will be able to check the flow of the module and purchase it as well by the end of next week.
"