The terminator does not support hot keys for changing the opacity of the background or color:
In my opinion, rewriting the configuration file on the fly is the wrong way to achieve what you want. A much better way would be the dbus we started introducing. It is designed to allow things working inside the terminal to communicate with the terminator and send commands that will affect the terminal. For now, he only exposes teams for separation, but in the course of time I hope that we will be able to expand it includes such things as colors and transparency, etc.
https://answers.launchpad.net/terminator/+question/173257
CompizConfig allows you to change the opacity of a window using a keyboard shortcut. The effect is different from the opacity of the Terminator background, but for me it's good enough - I want to look into the web page behind my terminal.
sudo apt-get install compizconfig-settings-manager
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