The old auctionhouse had a resetbutton to reset the select category, filter and searchtextbox.
Is it possible to add such a button again into the auctionhouseframe near the searchfield?

There's a button to reset the filter

I know, I mean a button to reset everything.
Close and unselect categories, clear searchfield und remove filter

Less clicks. If i would know how to do that, i would do.

I'm not sure why we need a button to do that?

As we avoid changing the default UI where possible this feature isn't likely to be implemented.