WBs do not seem to rescale on page width changes.
A mention of using right-click Open Web Block must help. Your:
To select the Web Block itself, click on the Web Block bar. A green outline around the whole Block shows that it is selected, and the Web Block bar is brighter.
says nothing.

WBs do not seem to Repeat on all pages at all.
This must be because they are LiveShare.
Again, explain a little.

I feel we require a blank Web block Wrapper and a blank Layout wrapper.
And the detail to combine and adjust.
I can see great potential for WBs but you've gone default in locking us out.

You seem to be creating a special Hell of wrappers, hiding everything Xara is good at.
Create you own Placeholder. Add detail in both Head and Body.
Then try right-click Edit widget.
All you get is access to the Body code. The Advanced button just dies.
I know how to get to the Head code. Will others? Do include a Body/Head toggle.
You also have to run off to another dialog window to stop the Placeholder image regenerating.

The Embed a Website widget is dead. As is Google Maps, Nabble & Bing.
I'm off to power down and back up again...
Before I go, the QR Code widget has still not been updated.

Also amazed your Blank website delivers MOver/MOff buttons that you have eschewed from the the Online Content Catalogue.
You still need to replace the NavBar approach.

Acorn