Could DO add the rar support just in preview?

Could DO add the rar support just in preview, so that we can have a preview of almost all Compress files's format with rar included? Although I know other rar supports like pack have not gotten the permission from rar's author yet..

I'm not sure what you mean.

Opus supports RAR the same as it supports any other archive format.

If you mean showing RAR files in the viewer pane, that only works for zip and nothing else because it's all Internet Explorer supports, and it's something added by the viewer pane's IE support. That's something the viewer does because it was simple to add by just adding one extension to the list of things IE is used to view. But it not particularly useful, IMO. If you want to look inside an archive, go inside the archive instead.

Yes, the viewer pane. could DO get any more improve to support more compress fotmat beside zip? Or can DO support other kind of compress fotmat viewer plugn not only of IE?