Put them in ~/.config/terminator/plugins/
Note: This assumes you are using terminator from Debian buster or newer that has been ported to python3. If not then you may need to use the version prior to pull request #5 - Available on the python2 tag: https://github.com/choffee/terminator-plugins/tree/python2
Online Search: searchplugin.py Open a new browser window with a google search for the selected text in a terminal