Espruino build for nRF52832 board with external low-frequency 32678 kHz crystal

I have a nRF52832 board equipped with an external low-frequency 32678 kHz crystal.
Is there a way to switch the low-frequency oscillator from:

• the internal RC oscillator to
  
• the external 32678 kHz crystal oscillator?
  ...to generate an espruino build?
  
  

I would like to use the external low-frequency 32678 kHz crystal to improve the board power consumption when used as a beacon.

The external low-frequency crystal is connected between P0.00/XL1 and P0.01/XL2 (see enclosed picture).
D0 and D1 are used on the Esprino MDBT42Q board to switch to DFU/reset modes and to light an LED.

• I believe that D0=P0.00/XL1 and D1=P0.01/XL2. Is this true?
  
• I believe there is an easy way to use different pins to switch to DFU/reset modes and to light an LED by creating a different board definition. Is that right?
  
• But I can't see any easy way to switch from the internal low-frequency RC oscillator to an external 32678 kHz crystal. Is there one?
  
  
  

1 Attachment

• nrf52832_ciaa_dcdc_schematic-01.svg