Testimonials have it's own Customizer section where you can edit Archive Title and Content, and Featured image.

Have you considered doing the same with Portfolio for consistent?
Portfolios also include a customizer section:

If you don't see it, you might be running into the problem that's discussed in #5143. Could you post some details about your setup there?
Thanks!
Oh, I only had add_theme_support( 'jetpack-portfolio' ).
When setting add_theme_support( 'jetpack-testimonial' ) it enables Testimonials in the Customizer. That's what I thought it would be enough for Portfolios also.
Thanks for this code which enables Portfolio section in the Customizer.
// Add theme support for portfolios.
add_theme_support( 'jetpack-portfolio', array(
'title' => true,
'content' => true,
'featured-image' => true,
) );
Most helpful comment
Oh, I only had
add_theme_support( 'jetpack-portfolio' ).When setting
add_theme_support( 'jetpack-testimonial' )it enables Testimonials in the Customizer. That's what I thought it would be enough for Portfolios also.Thanks for this code which enables Portfolio section in the Customizer.