It would be nice to have something like "icon only taskmanager" in plasma5. Then xfce users don't need to install some 3rd party docks/launchers.
I have never used Plasma, but "icon only taskmanager" sounds like showing only the icon of the app, and not the app name. It can be done with the current plugin disabling the option "Show button labels" under the panel item configuration.
The window buttons plugin has an option to only show icons, but it's not a dock and will very likely never become one. There are already a lot of docks out there that are small and good.