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, Insert>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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What do you mean by a "reference to more than a paragraph"? A reference is an address of an entity. There's no entity like "two paragraphs" in documents; so you cannot take address of that non-existing entity.
I suppose that you try to use cross-reference as a hack of inserting some content from some place into another place, using the reference's displayed text. Well - then you are using that for what it wasn't intended for... and it's impossible to use references that way you want.
Uhm...I see. But why «There's no entity like "two paragraphs" in documents»? It is technically impossible? However it should be useful...
And what about dde link?
Because then it would be impossible to even enumerate possible entities in a document: every possible two-paragraphs? every possible three-paragraphs? every possible four-paragraphs?... And what to do when you insert a new paragraph between the two? Should your entity be expanded to a three-paragraph entity? or should it exclude the last paragraph to stay two-paragraph entity? It all just doesn't make sense and would be strictly technical without any logical way to explain to users, with many impossible things, with uncountable bugs.
Wrt DDE - no idea; I only mentioned what I wanted to mention, and it doesn't make sense to demand what one can't answer (and you ask two different question in one Q, which isn't good).