Complex conditional logic for Webform field in YAML format
Nested states can be tricky. Make it two conditions:
visible:
  - ':input[name=&quot;field_a&quot;]':
      filled: true
    ':input[name=&quot;field_b&quot;]':
      filled: true
  - or
  - ':input[name=&quot;field_a&quot;]':
      filled: true
    ':input[name=&quot;field_c&quot;]':
      filled: true