Enable cccd to send indications

I need to enable a cccd 0x2902 starting indications,
Register for...block in BluetoothLe extension doesn't work.
The device characteristic send the bytes i need only thru indications not with notifications
I'm not aware if there is any trick to write directly, a way to implement directly java script to write the bytes to start the indication from the device .
nRF connect, nRF Logger give me all info correctly, but i don't find a way to start indications and manage it with the blocks of the Ble extension
Thank you