Huh? This is not an alternative devtools application, it's literally just a large collection of tutorials and tips on how to get the most out of your browser's devtools.
> So I don't understand the need for a website for this.
Perhaps read some of the website?
For instance the example for customising the output when inspecting your own object types: a view specific to your objects is something DevTools doesn't do out of the box (how could it when the devs know nothing of your objects?) though there is a way for you to tell it how to display them which few people know about. I for one was unaware until now.
Some of the examples seem a lot more like common knowledge (in fact you can derive some of the tips by just reading the screen in front of you while using DevTools) but that doesn't mean some people aren't unaware of the facility or are aware of it but have misunderstood and think it is less useful that it can actually be. For instance I know about the “Apply CSS styles to console messages” method, I've used it starting some time ago (though note: over use of things like this hinders more than it helps), but I image a lot of people don't because it isn't in the usual lists of console tips (which normally amount to illustrating the existence of console.warn(), console.table(), and similar methods).
Of course if you know everything about DevTools, or simply don't need/care to know more than you do, then the site genuinely isn't useful to you. But that doesn't mean it isn't useful to others.
> I see tips and tricks in the pane with issues and tips how to solve it.
I'm not seeing a Tips and Tricks pane so maybe we are not using the same browser, or you have an extension installed that is providing extra features.
There is What's New which does what this site is doing, just for brand new or newly updated features not those that have been around for some time.
The issues tab, but this is issues detected in the current page, not necessarily anything to do with DevTools..
The Issues panel in Chrome and Edge give you recommendations about how to make your website better.
This is different from devtoolstips.org which gives you tips for how to use DevTools better.
My browser doesn't have an "issues tab" nor do I see any tips.
Which browsers are you referring to?
If I would see those hints in the browser I still think the website is valuable as it shows me which functionalities I can use in other browsers too
Why the need for a new website for this?
What makes this useful over the issues tab inside the developer tools pane inside browsers?