How to handle the two different browsers..?

@Dave_Evers I think this will only help with multiple tabs in the same browser. Here, I think we need to handle two separate browsers of different types completely.

I think you’ll need to create two separate driver instances, then hand them off to Katalon when you need them:

// Open a new Chrome browser. You'll need to provide the path to your chromedriver.exe file on your machine:
System.setProperty("webdriver.chrome.driver", "C:/test/chromedriver.exe");
WebDriver chromeDriver = new ChromeDriver();
// Tell Katalon to use your Chrome driver:
DriverFactory.changeWebDriver(chromeDriver);

// do some work...

// Open a new Firefox browser. You'll need to provide the path to your geckodriver.exe file on your machine:
System.setProperty("webdriver.gecko.driver", "C:/test/geckodriver.exe");
WebDriver firefoxDriver = new FirefoxDriver();
// Tell Katalon to use your Firefox driver:
DriverFactory.changeWebDriver(firefoxDriver);

// do some work...

Here’s a page with some additional details:

https://docs.katalon.com/katalon-studio/docs/using_selenium_webdriver_katalon_studio.html#how-katalon-studio-uses-selenium-webdriver