Use template variable within a log query in Datadog

Question

In my LogStream widget I've the following log query

host:"/aws-glue/app/r/jobs/job_name"

the r letter should be variable based on the environment, thus I introduced a template variable $env_tag

host:"/aws-glue/app/$env_tag.value/jobs/job_name"

But it doesn't work ! how can we use template variable inside the query ? Thanks