Is it possible to change the date range for Google Analytics using 2 google sheet cells rather than the sidebar?
For example, if I don't want to expose the Supermetrics sidebar but do want to have the date ranges configurable for a sheet, how can I accomplish that?
All the query configurations that the sidebar uses are already stored in another hidden sheet called SupermetricsQueries. In there you can manually manipulate the settings, including referencing other cells for the configuration using standard Sheets functions. If you want to manipulate the dates, these are the relevant fields.
Do note that doing these kinds of changes will make it so you can't ever make changes to the query in the sidebar as doing so will cause it to overwrite your custom changes when the sidebar saves.
Is it possible to trigger a query refresh when these cells are updated?
Unfortunately, this is not possible - the refresh cannot be triggered outside of the Add-on. You you will need to manually refresh the query after updating the dates or schedule the refresh to happen automatically.