Sub-systems are used for large models with many blocks. They can be thought of as a container, or folder, in which you store blocks. A sub-system can contain other sub-systems which makes it possible to create hierarchies of matrices. Refer to sub-system and the model window.
The easiest way to organize the interaction matrix is to simply “drag” objects from one location to another:
If you right click the model window, you can select “Arrange Matrix…” from the popup menu.
A dialog window appears, with two lists and a drop down list. You “arrange” one sub-system at a time. Arranging means that you can change the order of objects on the matrix diagonal, you can hide objects and “unhide” objects. The right list contains all the blocks that are currently visible in the interaction matrix. The left list contains those that are not visible.