Need help interpreting a printer PS label
Per testing on https://newscrewdriver.com/2019/04/03/hp-inkjet-printer-power-supply-for-nec-vsl0010-a-vfd/ the usage for a similar HP supply with the same labeling suggests that you simply ground the pin with moon symbol to switch the Voltage out pin from on/32V to standby/12V.
As Tom suggested in the comments, a small resistor of 1k or 4.7k or so is better than just shorting to ground.
Your supply may be different so take this as a general hint.