This is super helpful when doing lighting tests or testing renders to any degree really. This is similar to the catalog column in Renderman’s ‘IT’(Image Tool) window if you have used that, where you can press page up and down to go through recent renders or arrow up and down to go through passes within those renders. To use slots in a similar fashion double click the arrow on the right side of the render window in Blender. Four tabs will pop out. Click on the ‘image’ tab. A pop out menu will appear with a ‘Render Slots’ drop down. In here you can arrow up and down to cycle through your recent renders. You can also add more slots or delete slots here as well.