Retrieve values for tag in cloudwatch

Greetings

I have a panel that displays the cpu consumption for each instances labeled with certain application tag (e.g. ‘app: my_app’). I did this defining a variable instance_id from a query

$instance	ec2_instance_attribute(us-east-1, InstanceId, { "tag:app": [ "my_app" ] })

However, I would like to allow the user to select the application it wants to display (there are many of them). Is there a way to retrieve the list of values for a certain tag?

Try:

ec2_instance_attribute(us-east-1, Tags.app, {})