\rw scripts only read -How to write?

I am new with Qubes OS i followed the setup instructions of proton vpn.

The problem:
How to add nft rules in the script as per suggested?

Add the rules below in /rw/config/qubes-firewall-user-script in the qube:

# Prevent the qube to forward traffic outside of the VPN
nft add rule qubes custom-forward oifname eth0 counter drop
nft add rule ip6 qubes custom-forward oifname eth0 counter drop

I can only read the script. Impossible to change its content.

With my first install I could. Now no more. Why?

I will be grateful for the help of the community to solve this issue.

Thank you in advance

What error do you have when you try to write the change?
You need to edit the file as root, e.g. using the root shell or running the command as user with sudo:

sudo nano /rw/config/qubes-firewall-user-script

Hi I got the message that the script is only to read. When trying to save as another file name in \rw.… Saving was not accepted. This on qubes running Debian 12. In the Qubes running Fedora 38 or 39 When saving the file i got the message that eas not saved snd truncated.

Thank you for your precious advice. I will have a try. I think it will work.

Hopefully my learning curve will improve with it.

Best regards