Update vc_icon and add your own to the list

functions.php

// 1- update map for vc_icons

add_action( 'vc_after_init', 'hubble_vc_icon_settings' );
function hubble_vc_icon_settings() {
    
    if ( ! WPBMap::exists('vc_icon') )
        return false;

    $vc_icon_map = WPBMap::getShortCode('vc_icon');
    //$params = $vc_icon_map['params'];
    $vc_icon_map['params'][0]['value'] = array(
                    __( 'Hubble Icons', 'hubble' ) => 'hubbleicons',
                    __( 'Font Awesome', 'hubble' ) => 'fontawesome',
                    __( 'Open Iconic', 'hubble' ) => 'openiconic',
                    __( 'Typicons', 'hubble' ) => 'typicons',
                    __( 'Entypo', 'hubble' ) => 'entypo',
                    __( 'Linecons', 'hubble' ) => 'linecons',
                    __( 'Mono Social', 'hubble' ) => 'monosocial',
                    __( 'Material', 'hubble' ) => 'material',
                );
    

    $insert_icon = array(
        array(
            'type' => 'iconpicker',
            'heading' => esc_html__( 'Icon', 'hubble' ),
            'param_name' => 'icon_hubbleicons',
            'value' => 'oli oli-heart', 
            'settings' => array(
                'emptyIcon' => false,
                'type' => 'hubbleicons',
                'iconsPerPage' => 4000,
            ),
            'dependency' => array(
                'element' => 'type',
                'value' => 'hubbleicons',
            ),
            'description' => esc_html__( 'Select icon from library.', 'hubble' ),
        )
    );
    array_splice( $vc_icon_map['params'], 1, 0, $insert_icon ); // splice in at position 3
    
    vc_map_update('vc_icon', 'params', $vc_icon_map['params']);
    
}

// 2- add your icon set
function hubble_iconpicker_type_hubbleicons($icons)
{
    $hubble_icons = array(
        array( 'oli oli-Orcid'=>'Orcid' ),
        array( 'oli oli-GoogleScholar'=>'GoogleScholar' ),
        array( 'oli oli-GoogleScholar2'=>'GoogleScholar2' ),
        array( 'oli oli-ResearchGate'=>'ResearchGate' ),
        array( 'oli oli-ResearchGate2'=>'ResearchGate2' ),
        array( 'oli oli-Mendeley'=>'Mendeley' )
        // ...
    );

    return array_merge( $icons, $hubble_icons );
}
add_filter( 'vc_iconpicker-type-hubbleicons', 'hubble_iconpicker_type_hubbleicons' );

// 3- enqueue your icon set ad admin
function hubble_enqueue_kelpericons_css($font){
    wp_register_style( 'kelpericons', HUBBLE_CSS . '/ol-icons.css',array(),HUBBLE_THEME_VERSION);
    wp_enqueue_style( 'kelpericons' );
}
add_action('admin_enqueue_scripts', 'hubble_enqueue_kelpericons_css');