Written by Alessio Piccoli and Cédric Leporcq. xfce4-windowck-plugin is a set of two plugins which allows you to put the maximized window title and windows buttons on the panel.
This code is derived from original 'Window Applets' from Andrej Belcijan.
Add the desired window headers plugins to the panel.
You can specify the behaviour and appearance in the proprieties dialog (controlled windows, show/hide buttons, theme, title formatting options…).
Please file bug reports or feature requests to github bug tracker.
How do I hide the window decorations on maximized windows on xfce ?
You can use a patch for xfwm4 available here : https://github.com/cedl38/xfwm4-titleless. Alternatively, you can try to use an external program like maximus (performance should be lower). There are also some xfwm4 themes with very thin border.