Is it possible to define an annotation which would appear in several panels?
I don’t think the builtin annotations can be shared between dashboards, but you can create a database that you use for annotations
Yes, it is possible in recent versions of Grafana - query by tag and you can show the same annotation on multiple panels or dashboards.
Here is an annotation query filtering by tags:
Here is the same annotation on multiple panels:
great, works fine. thanks