WiseJ Theme Builder.

Greetings again,
This URL   [https://docs.wisej.com/theme-builder/user-interface/preview] claims that the Theme Builder can
work against my specific soluition.

QUOTE: There are three built-in previews, but you can edit or create your own preview script
and you can preview your running application right in Theme Builder.

It appears that the three built-in “previews”, are just that, a generic way to view the formatting as stored
in the referenced theme file for the given “elements” defined in the theme file.

I’m asking     if somehow the Theme Builder can literally be pointed to an existing project or solution,
as it claims in the referenced theme builder documentation .?
“you can preview your running application right in Theme Builder”
or if that excerpt is actually attempting to instruct users to create examples
representative of their project’s constructs and throw them into the theme to preview….?

If it can be done please just toss me a URL and I’ll handle it.
Or please confirm my assumption above that I would have to harvest some samples from my solution and make a theme file from those.
The above cited document,  down in its information text box and immediately thereafter,  appears to additionally
claim that I would need to create my own “widgets” representing the stuff in my implementation of WiseJ
in order to “see” it affect my stuff specifically as the builder’s previews.

“ To show any widget in the preview panel you have to add it to root.
The preview panels in Theme Builder load the built-in preview scripts (JavaScript)
to show a predefined selection of controls and layouts. “