What is the screw size that holds SSD back plate? I lost mine.

Screw size is 6#32, length 7.5mm

How to sync ARGB of O11D XL to motherboard?

Push M button 7 times that comes to the 8th mode to sync the motherboard.

Can't find accessory box in O11D XL.

The accessory box is in the HDD tray.