unable to perform drag and drop to grouped windows in "window buttons"

Submitted by den..@..doo.fr

Assigned to Simon Steinbeiß @ochosi

Link to original bug (#7743)

Description

As it is today, there's no way to perform drag and drop with "window buttons", as soon as the target window is grouped. Proposal (KDE4 behaviour) : dragging a file to a button corresponding to grouped windows could prompt a menu containing these windows, so that dragging to one window in that menu raises it and one can perform drag and drop to it.

Version: 4.8.4