The only resource I can find for setting up secret_environment_variables is from this link
https://github.com/google-github-actions/deploy-cloud-functions but there is not much documented about how to add multiple secrets from secrets manager.
According to the document I set mine up as
secret_environment_variables: 'SECRET_NAME=projects/projectid/secrets/secretsid/versions/versionid'
This only seems to work for one secret. I tried different ways like stacking them, using comma separation, keeping them on 1 line. But I cannot find a way to get multiple variables and I cannot find documentation that explains the how.