Where can I find the Autosave file in Tekla Structural Designer?
Autosave is only used whilst you are in the software to protect against unforeseen issues whilst using the program.
The Autosave feature is controlled via the Home ribbon >Settings group > Settings command
In the unlikely event that the software crashes whilst in use, upon re-starting the program it will identify if an Autosave exists and offer to recover it.
This Autosave file/location can be determined via the registry (Start > Type "Regedit". Note you may require administration rights) and will relate to the version of the software you have installed.
You can determine the version you have installed via the 'i' icon to the far right of the ribbon as detailed in this guide here.
HKEY_CURRENT_USER\SOFTWARE\Tekla\Tekla Structural Designer\16.0.2.55\Autosave
If the file still exists at the specified location you could copy to your desktop and rename as .tsmd.