question

The code that is used to convey flowitems across a Processor is just Draw code that updates a flowitem's position on the Processor as time passes. Unfortunately, there is no option that tells the Processor to convey the flowitem in a different direction.

However, it is possible to change the rotation of the Processor so the flowitem will look like it is conveying in the opposite direction relative the rest of the objects in the model. You can do this in the Quick Properties of the Processor after it has been clicked on. You'll want to look at the Z rotation input, which is shown in this gif:

If you change that number from a 0.00 to 180, you'll see the Processor flip and the flowitem will convey from right to left, as shown here:

It is also possible to stop the animation from happening by double clicking on the Processor to open its Properties window and clearing the checkbox labelled "Convey Items Across Process Length". This will cause all the flowitems to be set in the center of the Processor during their Process Times. However, you could then create an Animation for the Processor in its Animation Editor that makes the flowitems do whatever you want.

This would require some understanding of how to use the Animator including how to use Draw Surrogates and might take some time to get working. If you are interested in learning about the Animator, feel free to look in the User Manual of the software, under the Modeling Tools section, then under the Animation Creator section to get a better idea on how to make custom animations. The Animation Creation section also includes two tutorials and the Advanced Concepts Tutorial even goes over using Components on a Processor to change flowitems that are being processed.