Firs of all.
You don’t really have access to physx within the engine unless you build the engine from source.
Replacing the dll to a baked editor is possible, I suppose, but it is very likely to break things… consider it a hack in fact. Also makes publishing harder because you don’t know if that DLL will get included as is or taken from something else (sort of likely actually).
Second of all.
What you want doesn’t require you to edit the physics system at all.
The system is already set up to allow you to adjust things on the fly.
Last.
As far as how you go about it.
Set up the objects to detect collision.
Set up an event for when the collision takes pace.
Check that the collided object is the one you want to remove the angular rotation from.
Override the angular values as you see fit.
I really don’t see anything that would make others tell you what you want is impossible.
In fact, you can just do all of that in blueprint without much of an issue.
Keep in mind that the angular value is still generating. You are just overriding it before it is applied.
As a whole, you probably shouldn’t be simulating the physics on this behavior, and why you want to we have no idea, but it doesn’t change the fact you should be able to without needing to edit anything at all.
At worse.
On the collision turn off simulate physics first.
Read in the values you want - maybe the object impact normal?
And manually apply only the momentum you need after turning simulate physics back on.
That’s assuming that for whatever reason the engine skips a beat and doesn’t manage to 0 out the momentum normally (which is unlikely as I had something similar set up without issues).
Also, anything else applying forces after the collision takes pace would normally rotate the item - which is what you wanted going by your post.
To do something else
like absolutely deny angular momentum after the collision until after the object is put to sleep, you would need to change the angular value on an ontick basis.