GREP text actions allow you to search and replace specific strings matching custom search patterns with other strings or patterns AFTER the merge process is completed. They are applied to all documents generated.

Go to Export > Extras > GREP text

Here you can activate or deactivate your configured GREP text replacements. To edit them click on the pen icon of each row, to add new ones click on the gear icon in the bottom right. This will take you to the preferences where you can add new actions or delete existing ones (Note: Predefined actions cannot be deleted. They are flagged with [System] at the end of the name):

GREP text actions are stored locally on your machine. Only activated actions will be added to project files.