Matlab simulink toolbox's counterpart in sagemath

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Hello, @hongyi-zhao!

Although it is not part of SageMath, there exists Modelica, and of course OpenModelica (https://www.openmodelica.org/). In particular, OpenModelica has the OMEdit graphical editor, which is very similar to the Simulink toolbox. One of the modules of OpenModelica (creatively enough called OMPython) allows you to interface with Python, and thus with SageMath.

On the other hand, the software Scilab (https://www.scilab.org/) has the Xcos toolbox, which is way more similar to Simulink, and also has a built-in compiler for Modelica. Scilab can be accessed from SageMath, but it is also a standalone software quite similar to Matlab.

I hope this helps!