I had the same wish and right now have three short cuts. (As a first step for a really good one...)

This line toggles object and grid snap at the same time:

script:var da = moi.drawingAids; da.gridSnap = !da.gridSnap; da.objectSnap = !da.objectSnap;

This line turns all snaps off and straight snap on:

script:var da = moi.drawingAids; da.gridSnap = false; da.objectSnap = false; da.straightSnap = true;

This line turns all snaps on:

script:var da = moi.drawingAids; da.gridSnap = true; da.objectSnap = true; da.straightSnap = true;