Canvas Preview - is an extension to the Powerful Preview asset, that allows you to preview your canvas prefabs.
Also, it's an example of what you can achive through the Powerful Preview asset.
1) It's not static, so it changes as the canvas changes (only Scaler right now).
2) It works with any UI element.
3) It handles children canvases.
1) Implement handling for any canvas components: layouts, filters, groups etc.
2) Canvas elements adding, removing and editing through the preview.