You can set up importers for any text file with any extension - the importer will not just recognize all Text files and know what to do with them.Open the Import Format Editor and go to this Tab
Here you can change the default Extension for the file from .csv to eg .TXT and then save the format - next time you drag and drop a TXT file it will use this formatter to import the data.
If you have a CSV Format defined and you get a TXT in the same format - then you can just change the extension and import the file with the csv importer.
If you run the Import command, you will see the txt file in the list of files when you point at the folder in which it resides. It will show up as unknown unless there is a formatter to read .TXT files already set up. You can right click the file and select the formatter to use to import the file.
Alan