Grafana, static drop down list / menu, value to query

Hi Guys, need a little help here with Grafana…

I am trying to make graph or single stat which will be showing result from the query. The challenge for me here is that part of the query must be one of the fixed values (numbers) which user would select from drop-down menu or list of option (somewhere in dashboard) like default value is 24 hours, possible to select 8 hours or 16 hours.

Is there such an option to create list / drop-down menu and user would select the value and this values goes to query ?

Example could be showing percentage © of available hours (A) vs. total hours (B), B would be selected from list of custom values by user on grafana dashboard i.e. query © = ( B - (subquerry A) / B) * 100

I use Grafana 6.5.2 and Influxdb 1.7.9.

Appreciate help, Salvq