Customize Dashboard

https://docs.thememylogin.com/article/92-using-pages

Thanks for your reply. Something I need to clarify that I would like to edit the dashboard UI. I would like to add some custom table or form in the dashboard but not only the menu. However, I can only see the shortcode.php is about the dashboard. Is there any files that I can edit to change the dashboard page?

You can certainly add stuff before or after the dashboard by creating the page and adding your content before or after the shortcode.