TabWalk

Use Alt+Shift with the left and right arrow keys to navigate your tabs in the order you've used them. Alt+Shift+◀ to go back, Alt+Shift+▶ to go forward. Simple like that.
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manifest.json
{
  "manifest_version": 2,
  "default_locale": "en",
  "name": "TabWalk",
  "applications": {
    "gecko": {
      "id": "TabWalk@maone.net",
      "strict_min_version": "57.0"
    }
  },
  "version": "1.2resigned1",
  "description": "__MSG_Description__",
  "icons": {
    "256": "img/icon256.png"
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "main.js"
    ]
  },
  "commands": {
    "prev": {
      "description": "Previously selected tab",
      "suggested_key": {
        "default": "Alt+Shift+Left"
      }
    },
    "next": {
      "description": "Next tab",
      "suggested_key": {
        "default": "Alt+Shift+Right"
      }
    }
  }
}