Hi Denis, 

thank you for your message. 

Unfortunately, we do not offer direct technical support for version 8 anymore, as you can see here:

https://helpcenter.websitex5.com/de/post/154824

https://helpcenter.websitex5.com/de/post/196325

Don't worry, by leaving this message as public, other users and the moderators will be able to reply and help you find  a solution. 

I wish you a lovely day. Kind regards.

Denis, what is the file type you wish to rename?

Is this site very large and is it online?

There have been great changes in WX5, perhaps rebuilding in the latest version may be the easiest option (& it comes with Incomedia support)?