A lot of what you are seeking is available in WC Vendors Pro- some in WC Vendors free.
1 – Can Admin restrict vendors from assigning more than one category to a product ? (each product can belong just to one category)
Not yet; but in our upcoming version 1.4.0 of WC Vendors Pro, which will be released in early April, you will be able to set category restrictions for vendors.
2 – Can vendors add external products ?
Yes- vendors have the option to list an external/affiliate product type. Both free and Pro.
3 – Is your plugin compatible with “Measurement Price Calculator” Plugin
I do not know if this needs some integration work to show up in the front end forms for the vendors or not– I will take a look at this plugin and see if I can get a hold of a copy to test. I m not familiar with the plugin at all at this time.
4 – I Want to order a new customized woocommerce shipping method so it can be used in a Split cart items ( vendor-wise split), i.e. from the same order via multiple shipping methods ( vendor-wise method).
Our Vendor shipping in WC Vendors Pro already does this.. could you be more specific about what you need for shipping?
5 – Does your plugin handle refunds ?
No- refunds would be handled and processed via the payment processor. As admin, you CAN mark commissions as reversed for orders that have been refunded.
6 – Can vendors invoice buyers?
Not exactly.. we do have plans to work with integrating an invoicing plugin, though full integration is not available form us at this time. I do believe some users have had a PDF invoicing plugin for WooCommerce integrated by a dev, though.
Vendors also have the option to list a product privately, and they can share the private listing link with the customer.
Please let us know if you have any further questions. 🙂