This is a somewhat silly example but it would be convenient. How would one define a variable x such that …

defineVariablesHere:
  x: city
axes:
  prompt:
    title: The Prompt
    values.prompt: forest near the ${city}
  negative_prompt:
    title: The Negative Prompt
    values.negative prompt: ${city}

…, or it might be used for PromptReplace where numerous PromptReplace operations share many similar substrings.

The only thing I find refers to placeholders and aliases, https://stackoverflow.com/questions/41620674/use-placeholders-in-yaml

Since I want to substitute into a string that won't work.