How can I define multiple tasks to run different commands?

Duplicate Question?

May be it is but I didn't find any answer. I reference some questions below. Which is related to my question. Question 1,Question 2,Question 3.

Question Overview:

In my task.json I wrote following code in which when I press ctrl + shift + B. Its shows output on my browser. Which works fine.

"version": "0.1.0",

"command": "chrome",

"windows": {
    "command": "C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe"
},

"args": ["index.html"]

In few days/ I am learning SASS and I need to integrate it with my VS Code. So, I found below configuration to add in tasks.json. Reference Site

{
"version": "0.1.0",
"command": "node-sass",
"isShellCommand": true,
"args": ["style.scss","style.css"]
}

Problem: When I put SASS configuration in my tasks.json file. It shows me some errors.

{
"version": "0.1.0",

"command": "chrome",

"windows": {
    "command": "C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe"
},

"args": ["index.html"],

"tasks": [
    {
        "taskName": "Transpile SASS into CSS", //my task name
        "command": "node-sass", //error, command is not allowed here
        "isShellCommand": true, //error, command is not allowed here
        "args": ["style.scss","style.css"]
    }
]

}

Question is how can I manage several tasks in VS Code. Please explain me what I am doing wrong.