File Manager: Upload Subirectories?

I want to be able to use the File Manager to upload new Wordpress theme/plugin files. The problem is that they often contain several subdirectories. From what I can see there is no way to include uploads of subdirectories (other than uploading the files in the subdirectories into the respective directory).

Am I missing something? Or is it simply not possible?

I’m a newbie with webmin/virtualmin but I think if you upload them/plugin as a zip file (WinRAR) and extract it after it will work normally.