The Nozzle Diam options only open for BOX, BOX+,UP300,X5 Cetus printer and some other models coming up. For the following printers, UP mini 2, UP mini 2 ES, UP Plus 2 and etc, the nozzle diameter is set to 0.4mm, and you can not change it.
The options for Layer Thickness can also be changed if the nozzle diam is changed. Check the Layer Thickness settings before starting a print.
How to change the nozzle diameter:
Open UP Studio software on your computer, click UP on the left side menu, click Maintenance, and then find Nozzle Diam to change the settings to the desired value.