Hello,
There is a built-in option to have a message displayed in this region- (wp admin > woocommerce > wc vendors > pro : Vendor Dashboard Notice)
And if you wish to alter that further, there is a template for that message area:
wp content/plugins/wcvendors-pro/templates/dashboard/dashboard-notice.php
Here’s an article to help you with properly moving & saving modified templates:
https://www.wcvendors.com/kb/changing-vendor-templates/