Unreal 5.1 is out and it doesn’t look like an official method to handle this exists yet. In a YouTube video from July 2021, @Minus_Kelvin suggested that this should be feasible at some point (citing “Audio Parameter Modulation” and “parameter buses” as examples of how it might be eventually be implemented). While that video covered the Early Access release of 5.0, it doesn’t seem that anything has changed. I’ve perused the MetaSound source code and I didn’t see anything about reading information back from MetaSound into the game thread (e.g. Blueprints).
I’d expect that once it is implemented, the interface will be similar to that of setting values in MetaSounds. That process is not currently documented in the manual. However, this learning tutorial describes the process.
Would love to find out that I’m wrong and that this does already work…