The documentation for the Form Builder Plugin suggests that it's possible to override or extend any existing field. However, the new upload field, introduced in version 3.84.0, seems to work differently in this regard.

This does not work for upload, but it works for the other fields:

// payload.config.ts

import { fields } from '@payloadcms/plugin-form-builder'

formBuilderPlugin({
  // ...
  fields: {
    upload: {
      ...fields.upload,
      labels: {
        singular: 'Custom Upload Field',
        plural: 'Custom Upload Fields',
      },
    },
  },
})

A suggestion is to update the documentation to include guidance on overriding or extending the upload field, as it appears to deviate from the rest.