Thank you for your answer. Your Custom Code works, I have put it in the Code Snippet plugin. The child terms are not selected anymore now. Great!
I highly recommend you to implement this function in the rework on the filter system, because this behaviour is a real problem if you want to precise, exact search for a parent category with many child terms, e.g. “shoe” as parent category and 30 child terms with different brands. Then the users have to uncheck ALL child terms if they just want to search for the parent category (Shoes)? Or did I get something wrongt?
I have got the impression that the site got a bit slow in reactions with the two modifications (first modification was here with Trigger Live Search: https://wp-dreams.com/forums/topic/how-trigger-live-search-after-custom-code-automatically-select-filter-values/). If you klick around a bit selecting different categories in the sidebar you can feel it. And this are just 8 (?) images, I wonder how it will be with 500 or 1000 images.
https://www.illuminatoren.com/downloads/
kind regards
Dave