Shortcodes have come up a few times in the years I have been maintaining Breadcrumb NavXT. Traditionally, they are a very poor way to call breadcrumb trails (manually adding them to every page/post that you want a breadcrumb trail is tedious). Now that the block editor exists (with block templates and block themes), it was decided that supporting the block editor with a Breadcrumb Trail block was a much better option. Breadcrumb NavXT can be called using the bcn_display() function, using the Breadcrumb Trail block, or the included widget.
Since shortcodes are on their way to being deprecated within WordPress, the core of Breadcrumb NavXT will not add shortcode support. You can always create your own shortcode in a site specific plugin that calls bcn_display(), there is also an extension to Breadcrumb NavXT that includes a shortcode.
