Earlier quoted context omitted.
I really hate that at some point in the past, KDE developers decided that they hated how deeply intuitive virtual desktops are and deprecated them in favor of something deeply unintuitive (Activities). Any issue or complaint mentioning it is shot down with "you're holding it wrong." Please just give virtual desktops first class support and lets forget about the Activities experiment. Most users hate it. The attitude…
Plasma/KDE's virtual desktops are working for me, as 3x3, 4x4 would be too small in the widget which shows in the 'taskbar', which is only 24 pixels high, here. Took me some time and asking in their irc-channel, but actually the basic setup is super-simple, and was too 'intuitive' for an old greybeard like me :-) You right-click on the launcher icon, or the systray and " Add or Manage Widgets ", then a window appears…
Then activate and position the Pager like I described above, and after that how it presents them.
Nonetheless I'm thinking that could be more integrated, and the pager could be larger, when howering the mouse pointer over it.