Breeze10 is a fork of KDE Breeze decoration with the following changes:

• The title-bar opacity is configurable.
• The separator between title-bar and window is removed.
• Opaqueness, opacity override is added to the exception list properties.
• Title-bar font is set indpendent from the KDE font settings (for use outside KDE).

Breeze10 was started from BreezeEnhanced (https://github.com/tsujan/BreezeEnhanced), a former fork of Breeze with title-bar translucency and blurring.

There are some dependencies you'll need to install. Some people suggested using the following commands:

sudo apt install git g++ extra-cmake-modules cmake gettext libkf5config-dev libkdecorations2-dev libqt5x11extras5-dev qtdeclarative5-dev libkf5guiaddons-dev libkf5configwidgets-dev libkf5windowsystem-dev libkf5coreaddons-dev libfftw3-dev

sudo pacman -S kdecoration qt5-declarative qt5-x11extras kcoreaddons kguiaddons kconfigwidgets kwindowsystem fftw cmake extra-cmake-modules

sudo zypper install git extra-cmake-modules libkdecoration2-devel kcoreaddons-devel kguiaddons-devel kconfig-devel kwindowsystem-devel ki18n-devel kconfigwidgets-devel libQt5DBus-devel libqt5-qtx11extras-devel fftw3-devel

The version number in the file NEWS shows the main version of KWin that is required for the compilation. Compilation should not be done against other versions of KWin!.

Open a terminal inside the source directory and do:

mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release -DKDE_INSTALL_LIBDIR=lib -DBUILD_TESTING=OFF -DKDE_INSTALL_USE_QT_SYS_PATHS=ON
make
sudo make install

After the intallation, restart KWin by logging out and in. Then, Breeze10 will appear in System Settings → Application Style → Window Decorations.

None so far.