Gosh, there are typos in the documentation. Bravo.
In the documentation I was reading, ExecuteNervousSystemFunction is mentioned multiple times, but the correct term is actually ExecuteGenericNervousSystemFunction.
Once I figured this out, I found the related documentation, which is also not linked on the page I was reading…
The correct link is: https://internetcomputer.org/docs/current/developer-docs/daos/sns/managing/making-proposals/#executegenericnervoussystemfunction
Moreover, once I got the correct spelling, I was able to find the references in the Candid files.
I’ll open a separate question for what is still unclear (here).