DVRs are references, and are automatically released when the VI hierarchy that created and "owns" it goes idle (stops executing). Commonly, the DVR just contains by-value objects, or LabVIEW references that are also automatically released, but an important use case of DVRs is wrapping a non-labview reference that must be properly cleaned-up. An example is an SQLite Connection pointer that must have a dll method called on it in order to release the database file it is holding open. Many dlls have similar pointers/handles that need to be properly closed. This is a headache for Programmers, who cannot rely on a stopped VI releasing its resources, often requiring restarts of LabVIEW to unload the dll.
A clean and easy solution to this problem would be to allow a "DVR Cleanup Callback VI" to be registered with the system when the DVR is created. That VI would be called if and only if the DVR is release because its calling VI hierarchy goes idle. This VI would contain the code to cleanup/close the contained non-LabVIEW references. Could have other uses, such as debugging.
I have developed multiple APIs that wrap non-LabVIEW dlls, and this feature would be a very significant help. Please consider it.