Currently on KDE 5 the KRunner dialogue brought up by Alt-F2 key, is not focused solely on desktop windows. It brings shortcuts to programs, search results etc, as well as the active desktop windows.
Other some alternative programs focused exclusively on window switching task, or can KRunner be configured to be restricted to desktop windows alone in certain contexts?
If I understand your question correctly, there are several routes that don't require the Alt+F2 route.
This basic method has a few possibilities itself which you can explore via System Settings > Window Management > Task Switcher. My preference is the very simple one shown below. On pressing Alt+Tab, I have a plain text display of open windows.
I keep the Alt key depressed and cycle through the choices with the Tab key. You can try various other options available on the Task Switcher page.
As shown in the image below, I've chosen "Text Only" from the dropdown and I have "Show selected window" unchecked. You may like something else.
Open System Settings > Desktop Behavior > Desktop Effects and type flip in the search bar at the top of the page. Activate Flip Switch.
If you click on the circled icon, you'll see a preview of what this can do. (It may take a while to load.)
If you decide you want to try it, open System Settings > Shortcuts > Global Shortcuts > System Settings and enter flip in the search bar (as before). Here, decide on a keyboard shortcut of choice to activate the Flip Switch or leave the existing choice in effect if there is one there. I've gone with Ctrl+MetaF10. Use Alt+Tab to cycle through the choices and press Enter when you've found the one you want. (Meta is the Super or Windows key.)
I won't go into detail here because the procedure to find it is the same as for Flip Switch. In this case, I went with Ctrl+F10 because that was already set up. Here, as you hover over individual windows, they're highlighted and clicking on the hovered one brings it into focus.
Screen EdgesAnother thing for you to explore is System Settings > Desktop Behavior > Screen Edges. Again, I'll not go into detail but just leave you with an image which I took after right-clicking on the top-right corner white square:
Edit:
To use many of the desktop effects, you must have compositing enabled and compositing is enabled by default if your system provides it.
To check, run qdbus org.kde.KWin /KWin supportInformation | grep -i composit
My system shows:
$ qdbus org.kde.KWin /KWin supportInformation | grep -i composit
Composite: yes; Version: 0x4
compositingMode: 1
useCompositing: true
compositingInitialized: true
windowsBlockCompositing: true
Compositing
Compositing is active
Compositing Type: OpenGL
$
By the way, you can toggle compositing on or off using Alt+Shift+F12.
You can configure what KRunner searches.
Rofi is dedicated to just switching: rofi -show window
You and bind that to Atl Space.
helmdialog in emacs. but I failed to express that in the question. I am trying to move to a 100% keyboard driven workflow even on graphical desktops, but the answer is a good answer, given the question I asked. – vfclists Oct 19 '18 at 13:00Alt+Tabroute. – DK Bose Oct 19 '18 at 13:06