KDE Dolphin cannot compress compressed files
Quoting: KDE Dolphin cannot compress compressed files —
If you think about it, Dolphin is pretty amazing. The file manager is pretty, slick, it comes with tons of extras and options, and so, it can do a great deal, often way more than other (rival) Linux file managers. It also handles compression natively, in a variety of formats. There are a few snags, as I've outlined above.
Should you ever desire to compress already compressed files - for whatever reason, including being able to send files over the email (as some mail clients block 7z, for instance), then, having the option to quickly package an archive within another archive is a good thing. I think Dolphin can easily be modified to always include the compress function. That's all really. Anyway, we're done. Take care.