Using kwin_x11 instead of Openbox would give us

• "Aero Snap"
• Resizable windows (at all edges)
• Resize icon in the bottom right
• Properly centered titles
• Qt theming
• Drop shadow rendering that does not appear before the rest of the window
• Nice animations on window resize
• "Magic lamp" effect when minimizing and un-minimizing windows, even to the Dock if it supports it
• "Exposé" overview of all open windows
• Stacked initial window placement Cascade = staircase-by-title
• ...while respecting centered Application splash screens
• Rounded corners at the top and sharp corners at the bottom (as we want)
• Rounded corners at the top disappear if windows are maximized or snapped to the top
• Many other cool features

As a result, the whole desktop feels much more modern (in a positive way).

But

• Need to find a way to build it with fewer dependencies (also see https://community.kde.org/KWin/Dependencies) - POTENTIAL SHOWSTOPPER
• Seems to draw in /usr/local/bin/kglobalaccel5 for global keyboard shortcuts such as Alt-Tab; this might mean that we should retire /usr/local/bin/lxqt-globalkeysd; configuration lives in ~/.config/kglobalshortcutsrc
• Can break Command+Space. When you click on the Desktop background and then type Command+Space, then it works. When another window is frontmost, then it is broken more often than not.

Notes

• /usr/local/etc/xdg/kwinrc can be used to set another window decoration and to set the order of the buttons in the window decoration; removing the need for kcmshell5
• Make titlebar metrics configurable tsujan/BreezeEnhanced#32 - a patched version of BreezeEnhanced is needed in order to configure aspects such as the height of the title bar in a fine-grained way
• /usr/local/etc/xdg/breezerc can be used to configure BreezeEnhanced, the possible values are explained in https://github.com/tsujan/BreezeEnhanced/blob/master/breezesettingsdata.kcfg

Starting with today's experimental ISO builds, the configuration for KWin is included on the ISO, but not KWin nor the BreezeEnhanced theme yet. For those who would try KWin on helloSystem, sudo pkg install -y plasma5-kwin, replace openbox with kwin_x11 in /usr/local/bin/start-hello, and build and install the BreezeEnhanced theme.