Rated 3 out of 5 stars

Leider muss man einen anderen Button installieren, schöner ist es einen Auswahlpfeil neben dem Original Button zu installieren. Siehe Kaosmos(AB IN TAB). Man kann auch nicht den Tagesplan von Lightning nur für das Adressbuch ausschalten.

Léirmheas ar leagan níos sine den bhreiseán seo (1.0). 

Well my German is to weak to understand everything but, yes, it is another button to install, I made this choice to let the user choose. Modifying the existing button with a preference don't let the user free to swap rapidly between opening the address-book in a tab or in a window.
Effectively Paolo "Kaosmos" has already developed an add-on doing this by adding an arrowscrollbox under the default button (as I understand) : https://nic-nac-project.org/~kaosmos/index-en.html#abintab. For the incompatibility with lightning please ask in english (or french).