We recommend downloading the Cubase Setup guide for the GS-R24 as a starting place for creating a custom MIDI Map, this can be downloaded from the documents section on the GS-R24 website.
https://www.allen-heath.com/ahproducts/gs-r24/
To assign the Jog wheel:
Follow the Cubase setup guide to assign the GS-R24 MIDI controls, in the Cubase Device Setup > Generic Remote window, there is a heading titled 'Flags', once the jog wheel has been assigned to the designated control in Cubase, you will need to ensure the 'Flags' setting is set to 'Transmit, Receive and Relative' for that control.