Hello
The feature to add the testimonial section with a shortcode is not available in the theme and you can set the the testimonial from the customizer section by going to Admin Panel > Appearance > Customize > Homepage section > Testimonial as of now.
Screenshot : https://prnt.sc/p11pmc
However, if you still want this feature in your side, you can refer to hire our customizer service.
Hoping for your kind consideration.
Regards!