New Docking - Margins - Padding section

Dear All,

Hoping you are all doing fine.

Something is not clear for me regarding the new Docking - Margins - Padding section.

Question #1
Indeed, I make duplicates on a Box twice, attached on 3 different Section I a have three different layouts on them, knowing that the render is the same for the 3 Boxes.

Original
Wix Docking 1

Duplicate #1
Wix Docking 2

Duplicate #2
Wix Docking 3

What the blue background stands for?

Question #2
I noticed that now it is impossible to align to left and right in the same time. Below from former project.

From former project
Wix Docking 4

Thank you for your replies.

Best regards,
Domivax