- Make creative tab
When releasing jars, do not include the dev stuff. See Create's docs about that here: Be sure to depend on Create, and crash if it's not present. https://wiki.createmod.net/developers/depend-on-create/neoforge-1.21.1#development-environment-dependency
Datagen must be run to include things like block properties. This is done with Gradle > mod development > runData.
Make sure this completes without any errors.
To build a jar file, run the task with Gradle > build > jar.