There is no option to merge .dat files in TNG. You can import the extension list, refer to forum post:
How do I import extensions from a file into TNG?
You can export the extension of the 'tngext.dat' file you want to merge to CSV. Follow these steps:
- Go to the 'Reports' page.
- Select the 'Extension Listing' under the 'System Reports' section.
- Use 'Preview' to see if all extensions are listed. If so, close the report and then use 'Export CSV'.
- You will now get the option to save to CSV. This is a comman delimited CSV file. Each column entry is in double quotes and seperated by a ','. You can edit this file in a plain text editor. Remove the double quotes and replace the ',' with a '|'.
- Once in the correct format, use the import extensions option, refer to post:
How do I import extensions from a file into TNG?