How to "redecorate" windows?

Strangely, by default, there is no toggle to decorate/undecorate a window.

You need to do one of two things: either define a keybinding to toggle or use the shortcut key to redisplay the window menu.

Lets examine option 1

To do this:

1. Open lxterminal and run:

   leafpad ~/.config/openbox/lubuntu-rc.xml
   

2. Search for the first instance of <keybinding>.

3. Then add the following keybinding:

   

   <keybind key="W-A-D">
     <action name="ToggleDecorations"></action>
   </keybind>
   

4. Now run:

   openbox --reconfigure
   

   to make your changes effective (alternatively, you can logout and login).

5. You'll be able to toggle the decoration using Meta+Alt+D.

   The Windows key is also another name for Meta.

Lets also examine option 2

Thanks to Glutanimate.

Pressing Alt+Space will display the window submenu where you can select Un/Decorate. Obviously this doesn't need a keybinding, but it's nice to have a toggle option to quickly turn the titlebar on/off.

I have just managed to invoke the Openbox' context menu on an undecorated window by right-clicking the bottom edge of the window. It's just that you need to right-click as soon as the resize cursor is displayed. The previous tricks did not work for me because there was a virtual Windows machine inside the window, so it was catching the Alt+space key combination...

You could make it permanent via configuration file:///~/.config/openbox/lubuntu-rc.xml

<applications>  
  <application class="*">
      <maximized>true</maximized>
      <decor>no</decor>
  </application>
</applications>

Reference: https://bbs.archlinux.org/viewtopic.php?id=82924 (#2)

Right click any window edge or corner or use Alt+Space. By "window edge", I mean the edges you would normally use to resize with a left mouse button drag. In this case, the right click brings up the menu to show or hide window decorations.