Using dashboard variables without timestamp

I want to use Elasticsearch data source purely for dashboard variables.
Problem is that those variables are quite static and I do not want to rewrite same data every 5 minutes so that variables timestamp would match dashboard time.
So it would be a good idea not to use any time stamp at all just a query for terms.
But Grafana do not support Elasticsearch data source without any time field.

Is there any way to work around this?

Why you need timestamp for dashboard variables? Timestamp makes sense only for TSDB data (e.g. for graphs, …), but dashboard queries shouldn’t produce TSDB usually.
See doc:

As I said I personally do not need timestamp, it’s Grafana which requires it. In variable query it is not reflected but somehow in background it is filtered by time range set on dashboard.
And also you can not add Elasticsearch data-source without specifying time field.