Child Field - Include in_all field:

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      When checked, the field is included in the definition of _all, which is the field specified by default in the Advanced panel. When unchecked, the field is not included.

      Inclusion means when query strings are used to specify searches, the text in the current field is searchable without the field name requiring a prefix. For Example, a search on description:modern can be accomplished simply by specifying the word ‘modern’. This is applicable for all query types and not just limited to query string query type.

      Example

      fts type mappings child field include in all
      "include in _all" will write a copy of the tokens generated for a particular field to the "_all" composite field. When this checkbox is checked, the resulting index will proportionately increase in size.

      Enabling this option results in larger indexes, so disable this option to always use field scoped queries in the search requests.