C# How to open a new tab in WebDriver from an async method?

Question

C++ / C#

I'm running some tests with a website using C# + Selenium. I run 4 tests at the same time in asynchronous mode:

Task t1 = Task.Run(() => Check1());
            Task t2 = Task.Run(() => Check2());
            Task t3 = Task.Run(() => Check3());
            Task t4 = Task.Run(() => Check3());
            await Task.WhenAll(t1, t2, t3, t4);

At the moment, in each of the methods Check1, Check2, etc, a separate browser is opened and the test takes place in it:

IWebDriver Browser1;
             ChromeDriverService service = ChromeDriverService.CreateDefaultService();
             service.HideCommandPromptWindow = true;
             ChromeOptions option = new ChromeOptions();
             option.AddArgument("--headless");
             Browser1 = new ChromeDriver(service, option);

After the end of the test, the browser is closed.
Everything works, everything is fine. In my program (WindowsForm) there is a field in which I enter some values, from which the test result can change. The problem is that now after each click of the "Check" button, I get 4 copies of the browser launched, running tests in them and closing the browser. This takes time.
I want to launch 4 copies of the browser when the program starts, and when I click on the "Check" button, I want to make sure that each test in its already open browser opens a new tab, runs tests in it and closes the tab. By this I want to reduce the time for the next tests if I change some input data.
Is there any example how best to do this?
Now if I declare a browser outside the asynchronous method, then this browser is not available to me in the asynchronous method and I cannot open a new tab for work in it.
Tell me, good people))