How can I add Next js environment variables to azure web app using azure key vault

I have a Nextjs application running on azure web app and I want to add an environment variables to the app through azure key vault. I have read so many documentaries and it’s said to be the safest.
Since I haven’t used key vault before, I’m having issues with the addition of env variables.
The nextjs variables is like this “NEXT_VARIABLE=‘jason123’”
The issue is that key vault secret does not access underscore (_), and this has been my problem. I’m not the dev guy though but is it advisable to ask the dev guy to change the even variables to the accepted key vault format or am I doing it the wrong way?