Adding New Mask Style
To add new Mask style in the Divi Builder follow the Actions Items.
Action Items
- Copy Mask Template (see bellow).
 - Replace 
NAME, all theET_Builder_Mask_NAMEin the template (3 places). - Replace 
TITLEin the template (2 places). - Replace 
PRIORITYin the template, lower number will make it show-up early in Mask Style Dropdown list in the VB. - Save in a new file, e.g: 
some-name.php, in this folder, add/commit to the repository. 
Tip:
- For 
NAME, if it's multiple words likeDiagonal Lines, use_to join, e.gDiagonal_Lines. - For 
filename, if it's multiple words likeDiagonal Lines, use-to join and make it lower case, e.gdiagonal-lines.php. - Once new 
filename.phpplaced in this folder, the new mask would automatically appear in the VB (just refresh). landscape,portraitandsquareshould only contain all tags inside the<svg></svg>file, e.g:
'landscape'            => '<path d="M28,28H56V56H28ZM0,0H28V28H0Z"/>',
Regular Mask Template:
<?php
/**
 * Background Mask Style - TITLE.
 *
 * @package Divi
 * @sub-package Builder
 * @since ??
 */
if ( ! defined( 'ABSPATH' ) ) {
	die( 'Direct access forbidden.' );
}
/**
 * Class ET_Builder_Mask_NAME
 *
 * @since ??
 */
class ET_Builder_Mask_NAME extends ET_Builder_Background_Mask_Style_Base {
	/**
	 * Configuration.
	 *
	 * @return array
	 */
	public function settings() {
		return array(
			'label'      => esc_html__( 'TITLE', 'et-builder' ),
			'svgContent' => array(
				'default'          => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'default-inverted' => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'rotated'          => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'rotated-inverted' => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
			),
			// Replace following PRIORITY with number (1-9) and uncomment to make it on top 9 list.
			// phpcs:ignore Squiz.PHP.CommentedOutCode.Found -- temporary comment.
			// 'priority'   => PRIORITY,
		);
	}
}
return new ET_Builder_Mask_NAME();
Extended Mask Template:
We're using following default viewBox settings for all masks (Code Ref).
	/**
	 * Default viewBox settings for Mask.
	 *
	 * @return string[]
	 */
	public function view_box_settings() {
		return array(
			'landscape' => '0 0 1920 1440',
			'portrait'  => '0 0 1920 2560',
			'square'    => '0 0 1920 1920',
			'thumbnail' => '0 0 1920 1440',
		);
	}
Also, we're using svgContent of square to show as thumbnail to display in Dropdown Style list in the VB.
In case a mask need any custom value for viewBox and/or custom thumbnail, can be done like following:
<?php
/**
 * Background Mask Style - TITLE.
 *
 * @package Divi
 * @sub-package Builder
 * @since ??
 */
if ( ! defined( 'ABSPATH' ) ) {
	die( 'Direct access forbidden.' );
}
/**
 * Class ET_Builder_Mask_NAME
 *
 * @since ??
 */
class ET_Builder_Mask_NAME extends ET_Builder_Background_Mask_Style_Base {
	/**
	 * Configuration.
	 *
	 * @return array
	 */
	public function settings() {
		return array(
			'label'      => esc_html__( 'TITLE', 'et-builder' ),
			'svgContent' => array(
				'default'          => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'default-inverted' => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'rotated'          => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				'rotated-inverted' => array(
					'landscape' => '',
					'portrait'  => '',
					'square'    => '',
				),
				// Following is optional, uncomment it if don't want to reuse landscape value.
				// 'thumbnail'        => '',
			),
			// Replace following PRIORITY with number (1-9) and uncomment to make it on top 9 list.
			// phpcs:ignore Squiz.PHP.CommentedOutCode.Found -- temporary comment.
			// 'priority'   => PRIORITY,
			// Following is optional, remove any number of them if you want to reuse global settings.
			'viewBox'    => array(
				'landscape' => '0 0 1920 1440',
				'portrait'  => '0 0 1920 2560',
				'square'    => '0 0 1920 1920',
				'thumbnail' => '0 0 1920 1440',
			),
		);
	}
}
return new ET_Builder_Mask_NAME();
The Code works as following:
- Look for 
viewBoxvalue from mask file, if not exists, global settings are used. - Look for 
thumbnailvalue fromsvgContentarray from mask file, if not exists,squarevalue is used. 
Last Updated: Feb 10, 2022.