It is a little frustrating to have these processor groups limited to 64 threads per group in Windows, relying on the developers of applications (like NI) to modify their code get optimal performance... Hopefully NI will make LabVIEW processor group aware in the near future.
There is some good news though. It seems that the company Bitsum - which develops the utility Process Lasso, a very useful program for Windows thread management and optimisation - has just released Process Lasso v9.7 with a feature called "Process Group Extender". I am unsure however whether it is included in the free version of Process Lasso. The blog post describing this new feature can be found here. The algorithm of this new feature is open source and can be found on GitHub.
In any case, it might be worth a try to see if it functions properly with LabVIEW. Hopefully you can get more performance out of your code by properly leveraging your multiple high-core-count CPUs with this utility.
Search LabVIEW like a graph! 