look into the networksetup command line tool.
I did that eben before jumping to Ventura because I use a second set of DNS-settings to access BC from abroad. I used to do that via locations, now I have two little command line apps on the desktop that switch DNS settings for both ethernet and Wi-Fi and purge the DNS cache after doing so.
For dummies: Use automator, use only one step for the app: shell-script. Insert lines you googled that change the settings. Export as application. Yes, a text editor will do as well but this is the “it just works (kinda)” way for non-programmers.