Skype application uses two types of notification:
In Vivaldi if Web Skype is used in Tab or Web Panel only 2 type of notification is used.
According to the following resources:
Stackoverflow - How do I make a Chrome extension's window blink in the taskbar?
Stackoverflow - Show orange Windows taskbar icon orange when a Chrome Packaged app gets a notification
1 type of notification can be achieved with:
var appWindow = chrome.app.window.current(); appWindow.drawAttention();
Can it (1 type of notification) be done for Web Skype (or any other) in Vivaldi ?