Hi,
1. Vendors can only edit their own products. Only the main vendor (you) can edit all products (like you can do in the backend).
2. HikaMarket have an option in order to change the "vendor root category". For the moment you can't specify several categories but it is a feature in our TODO list.
3. In HikaShop 2.2.0 we introduce the multi-shipping feature. HikaMarket adds a new restriction option called "vendor". By setting a vendor restriction (for the moment you have to specify the "vendor id") the shipping method will only be available for the selected vendor.
4. In order to display the vendor products, you have to use a "product listing" module with the option "synchronize".
In the vendor page this module will be synchronize with the current vendor. At this moment, by creating a menu which point to the vendor page, you will have your vendor product listing with a simple URL.
We are working and thinking about improving the vendor listing and this vendor product listing. Do not hesitate to give us your feedback so we can "use" it during the implementation and the product could support your requirements.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.