Where is New Interface PREVIEW on Create?

This is not yet available in the new M-Files Desktop but is in the plans to be added later when we improve the drag & drop operations in general.

It's on this year's roadmap, we don't have a more specific estimate yet. You can track the status via M-Files Client Feature Comparison which is updated regularly as development plans evolve. This feature is listed as "Show preview and metadata card side by side during object creation".