There are few reasons to add a 'manual' activity into the gradebook. The unit may have activities that exist outside of LEO, such as a presentation, or a simulation assessment. If nothing is submitted through LEO it may be useful to create a manual item, so that the lecturer can still place the grade/mark and any comments into the LEO gradebook directly.
Another reason to create a manual item, is to hide the raw mark for a Turnitin assignment. A Turnitin assignment is only capable of displaying a numeric mark. While this mark can be displayed as a grade in gradebook, a student will still see the numerical mark in the Turnitin assignment submission inbox. The workaround is to NOT put the mark into Turnitin, and use the manual item to add the mark/grade into the gradebook. Comments and rubrics can still be used in Turnitin, but no mark should be attributed to those comments in Turnitin.
Please contact the Learning and Teaching Centre for professional development, resources and advice for your learning and teaching needs at ACU.