Thank you, I believe I have found the source file.
I have replaced it's contents with the plugin shortcode (left the original comment disabled). The file is: wp-content/themes/walker/framework/modules/search/templates/types/slide-from-header-bottom.php
I recommend copying over this fiel to the child theme, in case of update it should remain unchanged. You should be able to see the plugin search on the front-page now.Best,
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