Reference-able filter of infrastructure entities

User story

As an Instana user,
who is in the process of specifying a filter on a set of infrastructure entities,
in order to view these entities, to detect issues on them, or to configure maintenance windows on them,

I want to have a way to persist and reference the filter,
in a way that if I update the filter in one (central) place, the update is automatically propagated everywhere this filter is used within Instana (e.g., Maintenance Windows, Application Perspective configuration, issue trigger condition, etc.),

so that I can save time from having to redundantly create or update these filters in various places, or from having to fix errors I accidentally make when doing so.

Alternatives explored and their limitations

• Application Perspective (AP), despite their ability to be defined on infrastructure entities, cannot serve this use case. Since an AP is merely a filter on calls, it is "alive" only during specific times when calls are being made to / within the AP (and not when no calls are being made). Therefore, scoping maintenance windows on the basis of APs will not suppress infrastructure events triggered when no calls were made to the AP (which is undesirable).

• It is possible to save DFQ-based filters, and retrieve them in other places (e.g., Maintenance Windows, Custom Events, etc.) and thus save users from having to copy+paste the query. However, it is possible to save multiple DFQs using the same name (which is undesirable as it can lead to confusion). Also, changes made to the filter do not get propagated to where these saved filters are used.