Multiline attributes, rendered templates, or Xcom variables are not well supported in the admin GUI at present. Any values are treated as native HTML text() blocks and as such all formatting is lost. When passing structured data such as YAML in these variables, it makes a real mess of them.
Ideally, these values should keep their line-breaks and indentation.
This should only require having these code blocks wrapped in a <pre> block or setting `white-space: pre` on the class for the block.