Xcode – How do we use same WKWebView for multiple UITab

So how I see, your biggest problem, that why you want to reuse WKWebView on every tab is sharing cookies:

In this case, we can avoid reuse and create a kind of cookie manager:

// SharedCookieManager.swift


final class SharedCookieManager: NSObject {
    
    // Singleton manager
    static let `default` = SharedCookieManager()
    private override init() { super.init() }
    
    // All cookies taht we have on every WKWebView
    var cookies: Set<HTTPCookie> = []
    // Callback helping to observe changes in our set
    var cookieUpdateCallback: ((_ cookies: [HTTPCookie]) -> Void)?
    
    // Append method
    func appendCookies(_ cookies: [HTTPCookie]) {
        cookies.forEach({ [weak self] in
            self?.cookies.insert($0)
        })
    }
}

Use cases of our manager:

// FirstTabViewController.swift

class FirstTabViewController: UIViewController, WKHTTPCookieStoreObserver {
    
    var webView: WKWebView? {
        didSet {
            SharedCookieManager.default.cookieUpdateCallback = { [weak self] newCookies in
                self?.webView?.configuration.websiteDataStore.httpCookieStore.getAllCookies({ oldCookies in
                    Set(newCookies).symmetricDifference(oldCookies).forEach({
                        self?.webView?.configuration.websiteDataStore.httpCookieStore.setCookie($0, completionHandler: nil)
                    })
                    self?.webView?.reload()
                })
            }
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        WKWebsiteDataStore.default().httpCookieStore.add(self)
        let webView = WKWebView()
        
        SharedCookieManager.default.cookies.forEach({ [weak webView] in
            webView?.configuration.websiteDataStore.httpCookieStore.setCookie($0)
        })
    }
    
    func cookiesDidChange(in cookieStore: WKHTTPCookieStore) {
        cookieStore.getAllCookies({
            SharedCookieManager.default.appendCookies($0)
        })
    }
}

Same for every ViewController you use within TabBar

It’s not a "golden hammer" and I can’t say it would work for 100%, but you can try to play with this sample to reach your goals. Hope it will help.