Helpo de LibreOffice 7.5
Creates a master document from the current Writer document. A new sub-document is created at each occurrence of a chosen paragraph style or outline level in the source document.
The Navigator appears after you create a master document. To edit a sub-document, double-click the name of a sub-document in the Navigator.
Select the paragraph style or outline level that you want to use to separate the source document into sub-documents. By default a new document is created for every outline level 1.