Widget shortcode is, or i can better say was, a great plugin. But the last time it is not updated anymore.
Now you can not see the shortcode anymore in the widgets area.
Maybe they will update and we get the great plugin back or we have to search a new great one.
I had tried another plugin to use a widget in the gutenberg block editor on a page, however that plugin had some issues so was not ideal.
Widget shortcode enabled me to add my widget by copying the generated shortcode to the shortcode block in the block editor, resulting in the widget being displayed perfectly on the page.