Track Merged Rows
How do I keep track of which rows have been mail merged?
From the Google Docs Add-on
In Google Sheets, create a column and name it whatever you want, e.g. Merged.
In Google Docs, open the Options window by clicking the button in the Mail Merge sidebar.
Select the Merged column in the Track Merged Rows and Merge Specific Rows fields. This will allow the add-on to write the date/time that row was successfully merged in the Merged column and avoid merging rows which have already been merged.
Click Save to apply changes.
From the Google Sheets Add-on
When you start Mail Merge in Google Sheets, a column called Filter Rows to Merge will be automatically created for the sheet you want to merge data from.
When you complete a merge, the add-on will automatically enter the date/time of the merge in the Filter Rows to Merge column.
NOTE: To merge these rows again, you need to clear/delete the date/time values in the Filter Rows to Merge column.