You are right: etc/resolve.conf will be overwritten at every reboot.
Maybe you can edit /etc/systemd/resolved.conf and, at the beginning, decomment the line:
But, at first, please perform a system backup. This solution was for Ubuntu and has not tested in Manjaro.
I don’t have the linux skills yet to be able to guarantee that everything will be fine.
On my laptop, I would try. I like test and see whether or not it works.
It’s up to you.