Variable in Grafana Splunk metrics?

Hi Team. While using Grafana data source for Splunk… Is it possible to use $variable in Splunk/Search metrics or in any transformation filters? Or there is a way in Grafana panel just to enter a Splunk query code with a variable, similar to Explore mode? We have tried everything (!) to date. No option for Splunk plugin found so far. Please advise. Thank you.