Where can I change the nozzle diameter in Cura?
The best way forward is to go back to the Creality Ender 3 print profile, if so, you can use this answer. So, you can select the correct nozzle size instantly.

Why is mine missing?
But, if you created a new printer profile, that option is not available. This is because that option is not available in custom print profiles. In order to use that option, the printer profile requires a variants configuration option; e.g. "variants_name": "Nozzle Size"
for the Ender 3 profile and for Ultimaker printers that is "variants_name": "Print core"
as they use a printer nozzle core concept. In order to use "variants", the printer profile needs to be aware that variants are available (from the Cura wiki as linked below):
# Whether your machine has the possibility to choose different variants.
# If this is set to "true", you will see the variant selection menu in Cura for your machine.
# By variants, we meant nozzles. You can have some specific variant profiles defined in folder
# "resources/variants". See files there as examples.
"has_variants": true,
For more information on generating custom Cura printer profiles look into Cura wiki "Definition File Types and the Base Definition Files" and Cura wiki "Adding new machine profiles to Cura".
So if you're profile doesn't support variants we need to revisit:
Where can I change the nozzle diameter in Cura?
The nozzle diameter is part of the printer configuration, but, linked to the Line Width property. You therefor can set the line width to 1 mm to achieve the same. With respect to the nozzle diameter, it is also found for the custom printer layout using the following: with reference to version 4.13.0, the nozzle diameter is set in the machine setup. From the main menu go to Settings->Printer->Manage Printers.... Now select your printer (and activate it to be able to) select Machine Settings and go to the extruder tab sheet to change the nozzle diameter (option Nozzle size under nozzle settings).



If you change the setting of the nozzle size you will see that this updates the option "Line Width" of the Quality group print settings to the same size. E.g. after changing the 0.4 mm nozzle value to 0.6 mm you will find the line width value updated:
