The Openbox Window Manager is designed to be highly configurable and customisable. This includes the ability to create your own custom keybindings - that is combinations of key presses - to undertake virtually any action. This includes the ability to create keybindings that can be used to manually control the brightness of your screen.
Although the Manjaro Openbox flavour provides a user-friendly graphical interface that may be used to alter or create custom keybindings, as the intention is to bind control of the screen brightness to the actual keys designed for this purpose, in this instance it will be necessary to manually edit the Openbox rc.xml file. This file - amongst other essential functions - serves to store and enable keybindings in the Openbox environment.
Step 1: Opening the rc.xml File
You will need to first open your terminal in order to edit the rc.xml file. The syntax of the command to edit this is:
[text editor] ~/.config/openbox/rc.xml
For example, if you wish to edit the file within the terminal using nano (a standard terminal-based text editor) then enter:
Otherwise - if you have installed the full version of Manjaro (i.e. not the NET-Edition) - you may find it easier to use a text editor like Gedit or Leafpad instead. This will create and open the 99-manjaro.rules file up as a document, making it easier to read and edit. To use Gedit instead, the command is: