You can add the relationship matrix by selecting the section package > relationship matrix >
and adding {Matrix.Image}
This is however not recommended. In all but the most trivial cases this will result in an unreadable relationship matrix. It looks ugly and is useless.
A better idea is to create an SQL fragment and put the required info into a table. It isn't quite the same as a matrix, as you you only have a fixed number of columns, but you can at least convey the information in a readable (and searchable) way that looks professional.
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