How do I read the numbers shown in Stat RHI

I’m creating a custom debug window and I’d like to display the current triangles drawn on the UI.

I know that tricount is displayed in the list called by Stat RHI command, but how can I read that number in my BP or c++ code?

Anything from the stat commands make use of the Stats System.
I’m not certain that any of the stats are tracked (or are even included in the compilation?) in Shipping builds, as certainly the “Print String” nodes for displaying debug text isn’t included in Shipping (by default).

However, the specific stat that you’re after is STAT_RHITriangles, which is part of the group STATGROUP_RHI.
I’ve not tried reading any of the existing stats, but this post has some details on how they wrote the stats to file, so that might lead you in the right direction.