The Edi project ediproj links the data document xlsx, xls with the text document docx, doc, odt.
There are also additional settings stored in the ediproj file, like storage location of the latest mail merge.
The ediproj file is a text file in XML format.
Multiple mail merge layouts
Create a different docx and ediproj pair for a layout, e.g. one file pair for an easy layout, and another pair for an extended layout.
Link all ediproj with the same data source xlsx.
After opening one edproj or the other one, you can print different layouts - once an easy, once an extended one.
Multiple mail merge data sources
Create a different xlsx and ediproj pair for a data source, e.g. one pair for invoices from the 2022 and another pair for invoices from 2023.
Link all ediproj with the same docx.
This way you can select a different data range and create a serial letter always with the same layout.
Multiple layouts and multiple data sources
You can mix the above solutions and create your own configurations of ediproj, docx and xlsx.