Shortcode in template builder WP 5.8

Hello,

Is this a known issue: I’m editing the theme via the template builder new in wordpress 5.8. When i add a shortcode in the header part it doesn’t work, just [myshortcode] or [wpml_language_selector_widget] is showing.
Is there an easy way to undo the template when i don’t have other templates in the list?

greetings Tom