Looks like you solving the issue wrong way. 

If you have multiple servers that can listen for connections, and allowed to do so, and you just need one external address that would use any of them for the clients. I would recommend using HAProxy, it's a load balancer tool, which may work for HTTP, and for plain TCP as well. In this case, clients will use HAProxy's address and port, and it will establish a connection to one of the backends. It may check if the backend is available, use backup backends if all primary backends died, and many other features. I'm using this in one of the projects for years, for HTTP with thousands of concurrent users, and 10 backends.

The error says almost everything, you have a permission issue. While you have Windows, it's kind of a common issue.

You have to check permission flags. 

But, I would not recommend using Durable %SYS at all. I suppose you use it in development right now, so, no reasons to use Durable %SYS. Ready for development image should be prepared with Dockerfile.

This is explorer view, supposed to be only to view the source of code on the server and read-only. There are two ways

  • Preferable, store any code locally, and when you save it, it will upload to server and compile it there. If you already have some of your code on server, you can export it from the explorer view.
  • Use virtual filesystem named isfs, in this case, all of your code stored only on server. Documentation

You can find some useful videos on youtube on Developer Community channel, for instance

As Kai, already mentioned, this icon, will appear only if you have any folder opened. Such a folder is a kind of project in VSCode. And, while Server Explorer view, which can be opened available by this icon, is supposed to be as just a server explorer, without editing. So, there are no reasons to make it available until any project will be opened.

First of all, you have to open this .code-workspace file with VSCode, it should offer to do it if you did not. Next, path is relevant to .code-workspace file location, and should contain own .vscode/settings.json. If all conditions are met, but behaviour not expected, please fill the issue, with examples, and screenshots, I'll try to reproduce and find the solution.

Look at the project mentioned earlier.
This part

{
  "folders": [
    {
      "name": "main",
      "path": "."
    },
    {
      "name": "part1",
      "path": "part1"
    },{
      "name": "part2",
      "path": "part2"
    }
  ]
}

Mentions three folders, where part1 and part2 supposed to be used to connect to two different servers. And each folder, have own .vscode/settings.json, which contains own settings to the server.

VSCode-ObjectScript extension which I suppose you already use, support the way, to work at the same time with multiple connections. And Mathew, gives you an example how to configure it. Look at the project. Important file there is multi.code-workspace, it's a kind of project file for VSCode, where is defined two folders, and each of those folders has its own separate settings for InterSystems. So, it means each folder will have its own connection to its own server. And you can configure as many connections as you would like. With the next release, I think it will be available one more way how to achieve the same.