Add a Matrix node () under Definitions>Variable Utilities (if Group by Type is active; otherwise, directly under Definitions) to define a square matrix of variables. You add it by right-clicking the Definitions node and choosing Variable Utilities>Matrix or by right-clicking the Variable Utilities node and choosing Matrix.

You can define a Label for the node and a base Name for the matrix. For the Geometry Entity Selection, see About Selecting Geometric Entities.

In addition, the Settings window for a Matrix node contains the following section:

Choose a Matrix format: Full (the default), Symmetric, or Hermitian. For a symmetric or Hermitian matrix, you only enter the upper-triangular part of the matrix. A Hermitian matrix (or self-adjoint matrix) is a complex square matrix that is equal to its own conjugate transpose. From the Matrix size list, choose a matrix size from 1x1 to 9x9; then enter the matrix elements in the table below.

The matrix is available as a list of variables with names <name><i><j>, where <name> is the namespace set in the Name field, and <i> and <j> are integer indices. You can use individual components where variable expressions are allowed, but also evaluate all variables at once using a matrix evaluation node under Derived Values. For example, select T1 under Model>Component 1>Definitions>Matrix variables, if the matrix has been defined with the name T1 in Component 1.