I have just switched from Plasma 4 (Kubuntu 14.10 to) Plasma 5, and I miss the "Show Widget Dashboard" functionality. As far as I can tell, it was part of this package in 4. Thank you for considering this request!
Hi, the dashboard widget has been removed and replaced by the "Show desktop" functionality. We have found that the dashboard most of the time was only used to show the same widget set as on the desktop anyway. Sorry.
Hi, thank for your lightning-fast response and for the clarity. Most functionality is covered with "Show Desktop", though for example I would use the calculator on top of a document I was working on (still being able to read the figures there) which is not immediately possible with "show desktop". The aesthetics are also different as is the user experience (immersion). But in any case, I'm grateful to know the actual situation, and for all the other great features of the current package.