layout switch via one button for https://github.com/tekezo/Karabiner-Elements

karabiner.json

{
	"global": {
		"check_for_updates_on_startup": true,
		"show_in_menu_bar": false,
		"show_profile_name_in_menu_bar": false
	},
	"profiles": [{
		"complex_modifications": {
			"parameters": {
				"basic.simultaneous_threshold_milliseconds": 50,
				"basic.to_delayed_action_delay_milliseconds": 1000,
				"basic.to_if_alone_timeout_milliseconds": 500,
				"basic.to_if_held_down_threshold_milliseconds": 500
			},
			"rules": [{
				"description": "Change input layout by right commang (ru to en, en to ru)",
				"manipulators": [{
						"conditions": [{
							"input_sources": [{
								"language": "^ru$"
							}],
							"type": "input_source_if"
						}],
						"from": {
							"key_code": "right_command",
							"modifiers": {
								"optional": [
									"any"
								]
							}
						},
						"to": [{
							"select_input_source": {
								"language": "^en$"
							}
						}],
						"type": "basic"
					},
					{
						"conditions": [{
							"input_sources": [{
								"language": "^en$"
							}],
							"type": "input_source_if"
						}],
						"from": {
							"key_code": "right_command",
							"modifiers": {
								"optional": [
									"any"
								]
							}
						},
						"to": [{
							"select_input_source": {
								"language": "^ru$"
							}
						}],
						"type": "basic"
					}
				]
			}]
		},
		"devices": [{
			"disable_built_in_keyboard_if_exists": false,
			"fn_function_keys": [],
			"identifiers": {
				"is_keyboard": true,
				"is_pointing_device": false,
				"product_id": 627,
				"vendor_id": 1452
			},
			"ignore": false,
			"manipulate_caps_lock_led": true,
			"simple_modifications": []
		}],
		"fn_function_keys": [{
				"from": {
					"key_code": "f1"
				},
				"to": {
					"consumer_key_code": "display_brightness_decrement"
				}
			},
			{
				"from": {
					"key_code": "f2"
				},
				"to": {
					"consumer_key_code": "display_brightness_increment"
				}
			},
			{
				"from": {
					"key_code": "f3"
				},
				"to": {
					"key_code": "mission_control"
				}
			},
			{
				"from": {
					"key_code": "f4"
				},
				"to": {
					"key_code": "launchpad"
				}
			},
			{
				"from": {
					"key_code": "f5"
				},
				"to": {
					"key_code": "illumination_decrement"
				}
			},
			{
				"from": {
					"key_code": "f6"
				},
				"to": {
					"key_code": "illumination_increment"
				}
			},
			{
				"from": {
					"key_code": "f7"
				},
				"to": {
					"consumer_key_code": "rewind"
				}
			},
			{
				"from": {
					"key_code": "f8"
				},
				"to": {
					"consumer_key_code": "play_or_pause"
				}
			},
			{
				"from": {
					"key_code": "f9"
				},
				"to": {
					"consumer_key_code": "fastforward"
				}
			},
			{
				"from": {
					"key_code": "f10"
				},
				"to": {
					"consumer_key_code": "mute"
				}
			},
			{
				"from": {
					"key_code": "f11"
				},
				"to": {
					"consumer_key_code": "volume_decrement"
				}
			},
			{
				"from": {
					"key_code": "f12"
				},
				"to": {
					"consumer_key_code": "volume_increment"
				}
			}
		],
		"name": "Default profile",
		"selected": true,
		"simple_modifications": [],
		"virtual_hid_keyboard": {
			"caps_lock_delay_milliseconds": 0,
			"country_code": 0,
			"keyboard_type": "ansi"
		}
	}]
}