How to add header_checks in postfix with regex

[stb (Stephan Bauer)]

NethServer Version: 8.
Module: Mail

How would I go about to add regex header_check in postfix. For instance to hide User-Agent or IP in NethServer 8 just like in the post referring to NethServer 7:

Remove/hide client sender ip from postfix?

# cat /etc/e-smith/templates-custom/etc/postfix/header_checks /^Received:.*with ESMTPSA/ IGNORE /^X-Originating-IP:/ IGNORE /^X-Mailer:/ IGNORE /^Mime-Version:/ IGNORE # cat /etc/e-smith/templates-custom/etc/postfix/main.cf/90header-checks # # 90header-checks # mime_header_checks = regexp:/etc/postfix/header_checks header_checks = regexp:/etc/postfix/header_checks

I found the following dir to add something to main.cf but have not gotten it to work…
/home/mail1/.local/share/containers/storage/volumes/postfix-custom/_data/

Any ideas? Thanks!