Hi Filippo!

Toogle GridSnap:

script:moi.drawingAids.gridSnap = !moi.drawingAids.gridSnap;


and just in case you need the other "Snaps":


Toogle StraightSnap:

script:moi.drawingAids.straightSnap = !moi.drawingAids.straightSnap;


Toogle ObjectSnap:

script:moi.drawingAids.objectSnap = !moi.drawingAids.objectSnap;


I'm using them with F5, F6 and F7.

~ Marco