Post #1511: 
roaoao:
bpy.ops.wm.context_toggle
Ah thx, I was missing bpy.ops, no wonder why the panel doesn’t show up.
Great addon, save me a bunch of time modifying the menu script directly.
(by the way, using command mode did allow me to change icon, so perhaps it’s related to how bpy.types.ToolSettings.use_snap icon is determined in property mode)