I’m afraid there is no solution to the multi-paragraph cross-references paradigm. However, no offence intended, I think there is a flaw in your use of Writer features.
A cross/reference, per its name, is a short pointer to another part of the document. Traditionally, this is the page number, chapter number or an identifier (think of notes). To ease designate the correct piece in a page, we may copy part of that piece (this is the reference item in the dialog). This copy is a reminder for the whole topic.
If I understand correctly your need, you’d like to duplicate a set of paragraphs at several locations in your document. You want them to remain in sync, whatever the revisions in the master occurrence of the set. This is not a task for cross-references.
You must then use sections.
You create a section (“Model”) for your first text occurrence. This is where all edition will take place.
Where you want a copy of your “Model” section,
Section, check Link and select the “Model” section from the drop-down menu. Enable write-protection to ensure that you won’t accidentally make modification to its text and lose sync with “Model”.
I’ve tried to use that trick to import a section from an external Writer file. It seems to work but organising the original sections is quite tricky because boundaries are not clearly visible. This was easier in earlier releases if I remember correctly.
Consequently, even with master and sub-documents this can be done. But be careful.
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