Silvio,
Thank you for working with CodeMix.
Are you looking to rename a .css file to .scss and in turn update/rename all references of that file in that project? If yes, then currently rename does not support updating all the references of the CSS file. You will have to manually update the references after updating the file extension.
CodeMix is based on VSCode smarts and the rename behavior for CSS is the same in VSCode as well.
I tried couple of extensions for CSS but none of them are renaming all the references of the file. I have filed a report with the dev team to check if we can work on it. We will keep you posted about it soon.
Apologies for inconvenience caused.
–Swapna
Genuitec Support