Convert rendering a theme in the themes view to shapes to allow others to contribute to the output

[MikeAlhayek]

Is your feature request related to a problem? Please describe.

Today, there is no flexible way to contribute to the output of the Themes views.

For example, there is no way to inject "Customize" button next to the Enable/Disable button to allow customizing the appearance.

Describe the solution you'd like

Convert he concrete view of the Themes view to shapes so we can inject shapes into the output.