When I have multiple windows of the same application opened, they are grouped in the icon-only task manager. A click on the group presents all windows on the screen to select the one to be activated. In Unity (from where I switched from recently), a click activates the most recently used window of this application and only the second click presents the windows on the screen. As not all people will like this workflow, an option to allow this feature would be very useful. I guess it's a relatively small change, but would allow users switching from Unity to keep their habits (and I have seen in a recent OMG Ubuntu comment that I am not alone: http://www.omgubuntu.co.uk/2017/04/best-unity-desktop-features#comment-3274480565). Addition will be likely to be made here, if that helps: https://github.com/KDE/plasma-desktop/blob/master/applets/taskmanager/package/contents/code/tools.js#L100
Also, tell me if I can help with implementing this in some way (I'd like to!), although I am new to KDE development and would probably need a little introduction.
It's non-trivial to implement this, but generally a nice idea.
I would also like to see this behavior made an option in both Task Manager and Icons-Only Task Manager. Before I switched to KDE, I was using the default 'Ubuntu' desktop in Ubuntu 17.10 and higher, which includes Canonical's fork of the GNOME dash-to-dock plugin. That plugin can be configured to implement the behavior described by this bug. As this bug notes, by default Unity behaves this way. As a consultant programmer, I usually have between 5 and 8 separate Atom windows open because I switch projects throughout the day. But, I only work on one project at a time. So if I want to switch quickly between my code (Atom) and my browser (Chrome), my expectation is that when I raise Atom, I'm raising the most recently used window. I'm able to achieve this in the Task Switcher (System Settings > Task Switcher > Main > Content > Sort Order: Recently Used, [X] Only one window per application. So it would be great if I could achieve the same behavior by interacting with Task Manager with my mouse.
*** This bug has been marked as a duplicate of bug 370258 ***