Yes, the vendors can add grouped products within the marketplace from their own vendor panel using the Marketplace Grouped Product extension.
This feature will now allow the vendors to use simple, virtual, and downloadable products for creating the grouped products.
The vendor will have the Grouped product type visible under the product type for creating the grouped products. The vendor will select the product type and proceed further to add the grouped products.
After selecting the Grouped product type, the vendor will select the continue button which brings up another page where the vendor has to enter all the required information about the Grouped product.
On this page, the vendor will find the option to add the products for this grouped product. Lastly, save the product and the vendor is done creating the grouped product type from the vendor account panel.
Please do contact us for any further queries or requirements. You can also check our Magento 2 Extensions for additional features.