What is describe in the book works for me
---
title: example block
output: bookdown::html_document2
---
```{example}
This is a special block
```
and _bookdown.yml
language:
label:
exm: 'Exemplo '
I get

as it is working with html_document2, it should work also with any other bookdown format.
If you have an issue with that, please give us some details to reproduce on our side.