My problem is - I cannot create a book with multiple sections in HTML.
I'm following the Demo project, everything is working pretty well.
However the separation by Description and Sections doesn't show up. It still
showing the whole HTML page.

My guess:
As I see, the only difference between my and Demo project is the difference
in HTMPlug plugin.
The Demo collection has configuration "description_tags".
My collection has configuration "smart_block".

I wonder if my guess is correct?

And I'm not able to make this changes if I click on Format Plugin. There is
the empty green field I'm not able to type in.
Could someone help me to find a solution?

Thank you in advance

Galina