At the moment, if you want to disable or enable snapping to the grid, you need to go to Tools|Options|Impress/Draw Options, via the menus, and select or deselect it. This is silly. People need to be able to enable or disable snapping to the grid with the push of a toolbar button; and IIANM it's like that in Microsoft Office.
Already an existing UNO command is .uno:GridUse to toggle the Snap to Grid mode. It is available to customize as Toolbar, Menu item, Context Menu item, or Keyboard shortcut. And is available and checked enabled for Notebook Bar assemplages. Add it where you'd like to use it.
(In reply to V Stuart Foote from comment #1) > Add it where you'd like to use it. Oh, right you are. I was thrown off by the fact that it's not on the Drawing toolbar, nor in the optional buttons for the drawing toolbar. Will file a different bug then.