How to put function WordPress plugin Into Shortcode (One User Avatar)

I was able to find a solution to the problem. For anyone interested here it is below. What I did was add some variables to the global found from https://github.com/onedesigns/one-user-avatar/blob/main/includes/class-wp-user-avatar-shortcode.php as suggested by the author of the plugin. (Some may not be needed, but I have included them as I will be extending the shortcode functionality in the future).

After that, I introduced the following function: do_action( 'wpua_update', $valid_user->ID ); (always taken from the file I linked above).

Finally I added the code I was interested in the form tags and in ob_start (); - return ob_get_clean();

Furthermore, in the html code taken by the plugin it was necessary to add a few lines of php for the form to save everything. <? php wp_nonce_field ('update-user_'. $ user-> ID); ?> <? php submit_button (__ ('Update Profile', 'one-user-avatar')); ?>

Here is the final working code

//SHORTCODE UPLOAD BUTTON ONE-USER-AVATAR
function short_shortcode() {
    
//Global
global   $wpua_force_file_uploader, 
         $show_avatars, 
         $wpua_shortcode, 
         $wp_user_avatar, 
         $all_sizes, 
         $blog_id, 
         $post, 
         $wpdb, 
         $current_user, 
         $wp_user_avatar, 
         $wpua_allow_upload, 
         $wpua_edit_avatar, 
         $wpua_functions;   

//Default user is current user
$user = $current_user;

//Function
do_action( 'wpua_update', $user->ID );

  ob_start();
?>
    <form id="wpua-edit-<?php echo esc_attr( $user->ID ); ?>" class="wpua-edit" action="" method="post" enctype="multipart/form-data">
        <p id="<?php echo esc_attr(('add-new-user' == $user) ? 'wpua-upload-button' : 'wpua-upload-button-existing'); ?>">
         <input name="wpua-file" id="<?php echo esc_attr(('add-new-user' == $user) ? 'wpua-file' : 'wpua-file-existing'); ?>" type="file" />
         <button type="submit" class="button" id="<?php echo esc_attr(('add-new-user' == $user) ? 'wpua-upload' : 'wpua-upload-existing'); ?>" name="submit" value="<?php esc_html_e('Upload', 'one-user-avatar'); ?>">
         <?php esc_html_e('Upload', 'one-user-avatar'); ?></button>
        </p>
        <?php wp_nonce_field( 'update-user_' . $user->ID ); ?>
        <?php submit_button( __( 'Update Profile', 'one-user-avatar' ) ); ?>
    </form>
        
<?php
  return ob_get_clean();
}
add_shortcode('short', 'short_shortcode');