The To Workspace block typically writes data to the MATLAB® base workspace. For example, when you specify the variable name "simout" in the "To Workspace" block, the data is saved in the structure "out.simout". Possibly to avoid the error (Unrecognized function or variable "name of variable" ), try using plot(out.simout), rather than plot(simout).
It may be useful for you to save the workspace variables to a file (MAT-file), using the save function in order for you to use in multiple plots. You can also log this data into a MAT-file by changing the model configuration settings,ie. enabling the MAT-file logging parameter in Configuration Parameters.