Hello,
I have tested this on 5.4.4, 5.5.4, and 5.6.0, and was able to reproduce the issue you described regarding overridden graph parameters being reset to the defaults on all 3 versions. Interestingly, I did not encounter the issue described regarding not being able to override parameters on 5.5.4 and 5.6.0. This was the case with both the repro project and without.
In any case, I have put together a bug report for this, which can be tracked here if/when it’s approved for public visibility: Unreal Engine Issues and Bug Tracker (UE\-294736\). There is no ETA as priorities for bugs and features can shift at any time.
We don’t provide updates on UDN, but progress can be followed on that public issue tracker page.
Take care,
John