Vulcan/packages/custom/lib/custom_fields.js

// Custom Post Field

Posts.registerField({
  fieldName: 'customPostField',
  fieldSchema: {
    type: String,
    optional: true,
    editableBy: ["member", "admin"]
  }
});

// Custom Comment Field

Comments.registerField({
  fieldName: 'customCommentField',
  fieldSchema: {
    type: String,
    optional: true,
    editableBy: ["member", "admin"]
  }
});

// Custom User Field

Users.registerField({
  fieldName: 'customUserField',
  fieldSchema: {
    type: String,
    optional: true,
    editableBy: ["member", "admin"]
  }
});

// Custom Setting Field

Settings.registerField({
  fieldName: "customSettingsField",
  fieldSchema: {
    type: String,
    optional: true,
    autoform: {
      group: "customGroup"
    }
  }
});