So you would need two different builds of Espruino running separately on each CPU. If you want to use bluetooth in Espruino then you need a build for the network processor but its 256kb flash is quite small. The application processor is better but does not have radio.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
As I understand it those two 'cores' are not exactly cores in the sense of sharing ram, flash and hardware (like used e.g. in ESP32 or Raspberry Pico). They are basically two different CPUs sticked together each having its own ram and flash and hardware. See https://infocenter.nordicsemi.com/topic/ps_nrf5340/chapters/soc_overview/doc/soc_overview.html?cp=3_0_0_2_0#blockdiagram
So you would need two different builds of Espruino running separately on each CPU. If you want to use bluetooth in Espruino then you need a build for the network processor but its 256kb flash is quite small. The application processor is better but does not have radio.
Also another big issue is that the SDK for 5340 is completely different - it is based on Zephyr OS
see https://infocenter.nordicsemi.com/topic/struct_sdk/struct/sdk.html?cp=8
so it would basically need completely new port of Espruino.
52840 is much better fit for Espruino, nrf5340 brings almost no advantage and lot of complexity