Felipe Elia

Tihs plugin creates a new type of field into <a href="https://wordpress.org/plugins/custom-field-suite/" rel="ugc">Custom Field Suite</a>: the user can select any form generated with <a href="https://wordpress.org/plugins/contact-form-7/" rel="ugc">Contact Form 7</a>.
You can get the form HTML using <code>CFS()->get( 'form_field_id' )</code> or the form ID using <code>CFS()->get( 'form_field_id', get_the_ID(), array( 'format' => 'raw' ) )</code>.
Note: Obviously, this plugin requires both Custom Field Suite and Contact Form 7 to work.
You can contribute to the source code in the <a href="https://github.com/felipeelia/cfs-cf7" rel="nofollow ugc">GitHub page</a>.

CFS – Contact Form 7 Field

Contact Form 7 field for Custom Field Suite

JR Tashjian

Generates an admin-facing select box for selecting a form from Ninja Forms and outputs the selected ID with CFS()->get().

CFS – Ninja Forms Selector

The Ninja Forms field type for Custom Field Suite

CFS – Contact Form 7 Field vs CFS – Ninja Forms Selector