You can build a sketch from any Vensim model including a text-only model. To add model variables, you can use the Model Variable tool, the Add Workbench Var Status Bar button, or the Sketch Variable List. To use the Model Variable tool, select it, click on an empty space, and select the variable you want to enter. To use the Status Bar button, select the variable you want into the Workbench, click on the Status button Add Workbench Variable and click on the sketch where you want to add the variable. To use the Variable List, make it visible, click on the variable you want to add in the list then click on the sketch where you want to add it. The model variable is added with its causes shown as shadow variables.
Adding causal variables to existing variables is easy. Select the Model Variable tool and position the mouse over a shadow variable (one surrounded by < >). As you position the mouse over a shadow variable, the cursor will change shape from 
to 
. If you now click on the variable, it will be converted from a Shadow variable to a Defined (model) variable, and its causes will be added as shadow variables. Repeat this operation on each of the shadow variables (after you have repositioned them on the sketch). When the cause of a variable is already defined in the sketch, an arrow will be drawn from the cause and no shadow variable will be added. This provides a very easy method for constructing a diagram out of the equations for a model.
