### Discussed in https://github.com/quarto-dev/quarto-cli/discussions/3918

<div type='discussions-op-text'>

<sup>Originally posted by **ThierryO** January 10, 2023</sup>
With version 1.1.189 we could add custom variables to the book settings in `_quarto.yml` and use them in the template. The example below provided `$book.reportnr$` in the template.

```
book:
  title: my title
  reportnr: 99999
```

After upgrading to version 1.2.313 this results in an error `property name reportnr is invalid`. How can we pass custom variables to a template in an extension?</div>
cscheid
2023-01-10T15:40:05Z
cscheid
documentation enhancement
v1.4
open
Specify which portions of the YAML namespace are safe for extensions
https://github.com/quarto-dev/quarto-cli/issues/3919