VS Code 1.77 added the `runCommands` command, which is basically a macro that you can define right in your keybindings file by chaining multiple commands together. In this case I bound individual test runs, file-scoped tests, and full Rake tasks to command-R + modifiers. (The `m` CLI is the m gem, which allows running minitests by file and line)…

keybindings.json

[
  {
    "command": "runCommands",
    "key": "cmd-r",
    "args": {
      "commands": [
        "workbench.action.files.save",
        "workbench.action.terminal.focus",
        {
          "command": "workbench.action.terminal.sendSequence",
          "args": {
            "text": "bundle exec m ${relativeFile}:${lineNumber}\u000D"
          }
        },
        "workbench.action.focusActiveEditorGroup"
      ]
    }
  },
  {
    "command": "runCommands",
    "key": "cmd-shift-r",
    "args": {
      "commands": [
        "workbench.action.files.save",
        "workbench.action.terminal.focus",
        {
          "command": "workbench.action.terminal.sendSequence",
          "args": {
            "text": "bundle exec m ${relativeFile}\u000D"
          }
        },
        "workbench.action.focusActiveEditorGroup"
      ]
    }
  },
  {
    "command": "runCommands",
    "key": "cmd-alt-shift-r",
    "args": {
      "commands": [
        "workbench.action.files.save",
        "workbench.action.terminal.focus",
        {
          "command": "workbench.action.terminal.sendSequence",
          "args": {
            "text": "bundle exec rake\u000D"
          }
        },
        "workbench.action.focusActiveEditorGroup"
      ]
    }
  }
]