I always knew that temporary preview files would go into the (usually) hidden AppData folder. However, just by chance, I noticed that Studio will create a particular folder (never mind about its random name) every time you want to "View the Target document using the selected preview type (CTRL+Shift+P)", same as clicking on the icon below. This is the location in your computer: C:\Users\[UserName]\AppData\Local\Temp\SDLTempFileManager. Same location for any Studio version (2015, 2017, 2019).

In other words, while you are translating, every time you perform this operation you get a different folder with (usually) a Word document inside and that means you get to keep all the different versions created during your translation process. In addition, another cool way of previewing your translation is the "Bilingual Document HTML Preview" which will show in your default Internet browser (by pressing ALT-F-P-P). This is the location: C:\Users\[UserName]\AppData\Local\Temp\SDLTempFileManager\[RandomFolderName]\BilingualDocumentHtmlPreview.html.