There are various ways to create custom key bindings/mappings in Linux. This tutorial uses xbindkeys on Ubuntu.
xbindkeys is a program that allows you to launch shell commands with your keyboard or mouse under the X Window System. It links commands to keys or mouse buttons, using a configuration file.
I have a ThinkPad and my keyboard has one of those blue buttons. Might as well put it to good use. I take a lot of screenshots, I’ll use it for that.
apt-get install xbindkeys
Create a configuration file for xbindkeys
Identify the key to be used for launching the command
Press combination of keys or/and click under the window. You can use one of the two lines after "NoCommand" in $HOME/.xbindkeysrc to bind a key. "NoCommand" m:0x10 + c:156 Mod2 + XF86Launch1
Add the following key binding to the configuration file
"gnome-screenshot" m:0x10 + c:156
"gnome-screenshot --window --remove-border --effect=shadow" Mod2 + XF86Launch1
Autostart xbindkeys (without arguments) on login. One option is to use the “Startup Applications” tool.