methods.php

...
	/**
	 * Get all GiveWP donation forms
	 *
	 * @return array List of GiveWP forms
	 */
	public function list_forms() {
		$list = array( '' => __( 'Select a Form', GoodModules::$text_domain ) );

		$forms = get_posts( array(
			'post_type'      => 'give_forms',
			'posts_per_page' => - 1,
		) );

		foreach ( $forms as $form ) {
			$list[ $form->ID ] = $form->post_title;
		}

		return $list;
	}

	/**
	 * Build array of conditional settings.
	 *
	 * @return array settings applied to the toggle setting in register_module
	 */
	public function toggle_fields() {
		$toggle  = array();
		$form_ID = $this->settings->select_form_field;

		if ( GiveUtils::isLegacyForm( $form_ID ) ) {
			$toggle = array(
				$form_ID => array(
					'sections' => array(
						'form_settings',
					),
				),
			);
		}

		return $toggle;
	}
...

register-module.php

$give_forms = new CLGM_Give_Forms();

/**
 * Register the module and its form settings.
 */
FLBuilder::register_module( 'CLGM_Give_Forms', array(
	'form' => array( // Tab
		'title'    => __( 'General', GoodModules::$text_domain ), // Tab title
		'sections' => array( // Tab Sections
			'select_form'   => array( // Section
				'title'  => '', // Section Title
				'fields' => array( // Section Fields
					'select_form_field' => array(
						'type'    => 'select',
						'label'   => __( 'Select Form', GoodModules::$text_domain ),
						'default' => '',
						'options' => $give_forms->list_forms(),
						'toggle'  => $give_forms->toggle_fields(),
					),
				),
			),
			'form_settings' => array( // Section
...