I am thinking of adding an upload company registration certificate function when new seller sign up and before they continue to use as new seller, they need my approval as genuine seller. How do I do this?
If you want to show a note and link of a page for uploading files while the sellers register, you may customize template-tags.php which is located at “\wp-content\themes\dokan\includes\”. For better customization you can make a child theme and place your changes there.
And you can disable new seller from selling from Dokan > Settings > Selling Options.
And then you can use contact form 7 as Jason said.