Step 7 V5.5 is just that. Step 7 with STL/LAD/FBD.
When buying a car, it's the basic car in the catalog.
Step 7 Professional is more. This one (car) has most of the options selected.
Has SCL and GRAPH.
Usually also have a SUS.
You can buy Step 7 V5.5. Then SCL. Then GRAPH. Then the SUS. But it would be more expensive then buying the package.