Regarding Mapping

[radhiam]

while running the configuration.json file for the work items. do I have to add each fields for the Mapping?
what will happen if I'm not creating any customized fields in the process template & not adding any Mapping in the configuration.json?

[MrHinsh]

All fields are mapped out-of-the-box with no required configuration.

The custom fieldMapps are only used when you want to move data around. Maybe you have a field in the source that is different in the target.