I apologize, guess I could have stated that to begin with.
If you add additional surfaces or solids to the part file prior to creating a "Job", these extra pieces of geometry will be selected in the job by default. If however you create a "Job" after creating supplementary geometry the supplementary geometry will be automatically selected by default as part of the model.....anybody (solid or surface) can be added to the Jobs default model. The same is true in individual operations, if needed you can select "Model" from within an individual operation and select supplementary geometry. Geometry selected in an individual operation overrides the geometry selected in the "Job" model, so make sure you include the base geometry as well.
In this image you can see I’ve added two surfaces (red & green) that we will use in this example.
The two surfaces that I extruded I placed in the “Extensions” folder…just to keep things tidy. Upon creating or inserting addition geometry while in part mode, SolidWorks will create folders for “Solid Bodies” & “Surface Bodies” (upper portion on the feature tree). The newly created surface bodies “Surface extention1” & “Surface extention2” are found there.
The pre-existing “Job” & it’s defined “Model” remains un altered as the job was created and defined prior to the creation of the two surface bodies.
Creating a new “Job” after the surfaces were created you can see that the two surfaces bodies are automatically selected and included as part of the “Model”. These bodies can be easily removed from the default model by deleting them from the model selection.
Going back to the pre-existing Job (just the solid body is used as the default model). We will use an existing toolpath that is seen below to demonstrate how we can add the two extended surfaces in an individual operation.
In a duplicate operation select “Model” and select all bodies to be considered in the calculation. Don’t forget to include the base model in this case not just the additional geometry as what is selected here will override the default “Model” in the “Job” definition.
The resulting toolpath.
I hope this is help full and clarifies the issue further.