I see!
I think there is another way - build the APK, extract the manifest, edit it, return it to the APK (an APK file is essentially a zip file).
However, why not ask the Admob Extension developer to help you?
I see it is essential to use the latest version of the extension:
https://github.com/oseamiya/AdmobExtension/raw/main/admob-sdks/out/com.oseamiya.admobsdks.aix