TDL files are specially structured text files so you cannot just take a plain text and create a TDL file from it - unless it was formatted before. However you could copy and paste the data from the *.tdl and with some spreadsheet editor create a version in TDL format using the save as.. / export to.. function.
Convert Simple text file to Tab Delineated file format.
We found one software available in the database for this conversion.
Microsoft Windows software - convert txt to tdl on Windows
A popular spreadsheet application distributed with Microsoft Office suite
Convert from txt file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.