Hello,
The .tss is known as a Session File it contains the configuration of the oscilloscope and the currently captured waveform. You can use a session file to send a configuration and data to someone else. To open a session file you have two options, either open it on another MSO4/5/6 oscilloscope, or for off scope analysis use TekScope linked below.
For other ways to save data refer to Saving and Recalling Information starting on page 181 of the help document also linked below.
TekScope:
https://www.tek.com/en/products/software/tekscope-pc-analysis-software
MSO4/5/6 Help Document:
https://www.tek.com/en/manual/oscilloscope/456-series-mso-5-series-mso
