Is it possible to make the nRF5340 IC transmit a CW ?

You can look at this example:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html 

I did make a small modification of the above example that can setup a fixed modulated carrier without uart, in case it can be of use.

If you want an unmodulated carrier you can try to use test_config.type = UNMODULATED_TX, instead of MODULATED_TX.

Kenneth

You can look at this example:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html 

I did make a small modification of the above example that can setup a fixed modulated carrier without uart, in case it can be of use.

If you want an unmodulated carrier you can try to use test_config.type = UNMODULATED_TX, instead of MODULATED_TX.

Kenneth