https://codex.www.ads-software.com/Child_Themes#Using_functions.php just proves to me that what I was going to change in some mantra function (part of the theme-functions.php) is not possible to do without losing changes after parent update.
It doesn’t use “if ( ! function_exists …”, so it is not possible to make it “…pluggable —that is, replaceable by a child theme— by declaring them conditionally…”.
I have tried to add the modified function to the functions.php in the child theme and used “if ( ! function_exists …” in the parent theme-functions.php and it worked for me. The original parent function was replaced by the child function. But I realize that it will stop working after the parent upgrade.
