The xw4600 front panel 18 pin connector is called P5. The pinout is below (this has been posted in a previous thread)
Thermal+ and Thermal- go to a thermal sensor that measures air temperature as it enters the system. If they are not connected, the xw4600 fans will probably run at full speed and be noisy.
Do not connect anything to the CHASSIS pins.
Connecting a momentary switch between POWER_BUTTON# and GND will power up the system.