Currently, there is no way to determine the SDLXLIFF files on which version of Studio was used to save the files as latest.

It's hard to investigate when has problem with translation files, whether the SDLXLIFF had been translated on the right Studio version as expect.

Would it possible to add line of code somewhere in <file-info> or <sdl:filetype-info> of each SDLXLIFF when it was saved with information what was the Studio version?

Example: As value key as sample below in SDLXLIFF.

<file-info xmlns="http://sdl.com/FileTypes/SdlXliff/1.0">
<value key="SDL:FileId">f6c74718-b1b0-43be-a5e4-774ccb75e8a1</value>
<value key="SDL:CreationDate">08/14/2018 16:27:37</value>
<value key="SDL:OriginalFilePath">C:\Work\!Projects\AL_LK_03_001.json</value>
<value key="SDL:OriginalEncoding">utf-8</value>
<value key="EscapeUnicode">False</value>
</file-info>