Describe the bug
The use of 6.3.0-rc.9 is causing my Storybook to crash with a runtime error of

It seems like it is related to the use of code in parameters

export default {
  title: 'Components/Eyebrow',
  component: Eyebrow,

  param

By default ember-cli updates a number of the "app trees" to be from tests/dummy when developing an addon locally. We do this for app, styles, templates, public, and tests trees (handled inside lib/broccoli/ember-addon.js).

Unfortunately, we do not forward the apps vendor tree to tests/dummy/. This means that our addon's treeForVendor is called, but then subsequently clobbered by the "apps

Is your feature request related to a problem? Please describe.
I understand Ember Inspector is for the development and Debugging phase. And I am of the opinion that, having access to the private (by convention, underscore prefixed) fields/property is a very useful feature when hunting for problems like why a certain computed property based on other field and property have an unexpected value.

It got lost early in some v4 release candidate. Original content could be found here: https://github.com/kaliber5/ember-bootstrap/blob/b711738bba95fd9523e573e5e314f4cf7257f93f/addon/components/base/bs-button.js#L183-L191 It could be used as a starter.

Reported by @rwwagner90 here: kaliber5/ember-bootstrap#1110 (comment)