As Systems of PDEs describes, toolbox functions can address the case of systems of N PDEs. How do you represent the coefficients of your PDE in the correct form? In general, an elliptic system is
The notation means the N-by-1 matrix with (i,1)-component
Other problems with N > 1 are the parabolic system
the hyperbolic system
and the eigenvalue system
To solve a PDE using this toolbox, you convert your problem into one of the forms the toolbox accepts. Then express your problem coefficients in a form the toolbox accepts.