For the Keylab series there is something about split in the manual, but not for Essentiel version. That indicates this function is'nt avaible for you.
According to the MIDI Cobtrol Center manual "3.2.1. The Project tab" not all devices have access to the needed Project Tab.
You can contact Arturia support directly about this, if needed.
Keep in mind, that some DAWS and many vendores applications including Arturias Analog Lab and some of Arturias individual applications provide split features, that does'nt require a keyboard that have split options.