I can set it by hand in Preferences and it works but I can’t find a way to do it from Python.
keymap = key_config.keymaps.new(name='Mesh', space_type='VIEW_3D')
keymap_item = keymap.keymap_items.new('wm.tool_set_by_id', type='L', value='PRESS', ctrl=True, shift=True)
keymap_item.properties['name'] = 'addon.tool_edit'
addon_keymaps.append((keymap, keymap_item))
The only thing that has worked for me is to use name=‘3D View’ but then that interferes with my other tool’s shortcut in Object Mode. I have two tools, one for Object Mode and one for Edit Mode and I’d like them both to have the same shortcut.