How to... set additional magnetic points/lines to a shape?

[Friedrich W. H. Kossebau]

Hi,

one thing you might have noticed in the barcode shape is that there is a 
margin around the actual content for at least the QR and DataMatrix types. 
This is because for these some kind of 'quiet zone' is defined, so the pattern 
can be more easily detected. Just, if one layouts some document/slide/whatever 
she might want to align the actual content in the layout, for a nicer look and 
as the 'quiet zone' is already there due to the layout.

So, I would like to show the needed margins for the 'quiet zone' in the 
editor, but have the actual content snap to the grid or guides as well. How 
can I get there?

Cheers
Friedrich