How to disable vue/multi-word-component-names eslint rule for just one .vue file?

In your case, you can replace

'vue/multi-word-component-names': 'off'

with:

'vue/multi-word-component-names': ['error', {
  'ignores': ['default']
}]

this will set the rule to ‘allow’ for all files named ‘default’

you can read more about it here: https://eslint.vuejs.org/rules/multi-word-component-names.html