Kvantum is customizable SVG-based theme engine for Qt5 that comes with a variety of built-in styles, including versions of some of popular GTK+ themes such as Adapta, Arc, Ambiance, Materia.
To install Kvantum install the package
kvantum-manjaro in your favorite package manager or using the command:
pamac install kvantum-manjaro
Kvantum Manager can be used to manage your kvantum themes and settings.
This also includes 'hacks' such as transparent Dolphin view, blur, icon sizes, and more.