Meta+Shift+<0..9> shortcuts by default, but these defaults are not working yet!
Plasma already has Meta+<0..9> keyboard shortcuts to "activate" the applications in the taskbar/task manager. But if an application is the taskbar already has a window open, that shortcut will show and focus that window, and not open a new window (which is OK).
These Meta+Shift+<0..9> shortcuts would allow opening a new window when there is already a window open of that application using only the keyboard (in the icon-only task manager). Windows and some other Linux desktops also have these shortcuts.
With these changes, the Meta+Shift+1..9 shortcuts actually appear in the Keyboard Shortcuts settings, but the default shortcuts are not working. If I then manually assign the combination Meta+Shift+1 in the Keyboard Shortcuts settings, it actually shows as Meta+! (for my keyboard), and then the shortcut works. I'm not knowledgeable enough in Qt/KDE to fix that.