Ubuntu gives us easy way to bind a shortcut key with any program. Suppose you want to open Firefox when Win+G are pressed. Or press Win+H to open text editor. This can be achieved by using internal Ubuntu System Settings. You don’t need to install any external program.

Normal Applications

Open System Settings (gear logo) > Keyboard > Shortcuts > press Custom Shortcuts > press plus (+) button. Here, name your shortcut i.e. Mozilla Firefox and type the command. You must know the command exactly, e.g firefox is command for Mozilla Firefox. Another command examples such as brasero for Brasero, thunderbird for Mozilla Thunderbird, evince for Evince, and so on. Remember that they are case sensitive. Now, click the line you’ve created and press the keys i.e. Win+H.

Commands

Suppose you want to execute a command line from keyboard shortcut. For example, turning the brightness down/up. Of course, there are thousands and more possible commands to bind with shortcut key. Imagine you can pipe or redirect somethings by just pressing shortcut key. To do it, do the same like normal applications and type the command line i.e. xrandr –output LVDS1 –brightness 0.5 to turn brightness down and xrandr –output LVDS1 –brightness 1 to turn it up. Again, after typing a command, click the line you’ve created (see right panel) and bind the keys i.e. Win+J.

Sumber: https://www.ubuntubuzz.com/2015/10/custom-keyboard-shortcut-key-ubuntu.html#more