I tried modifying global keyboard shotcuts (Kwin): go to Desktop X, go to Desktop right/left.
When I try the keys nothing happens. Maybe there's a visually application to do that? (create new workspaces / switch between them)
If you are using the new Plasma5, some say it has problems with keyboard shortcuts (not that I've noticed).
You can easily change workspace by using the "Desktop grid" effect. Once you have enabled it in "Desktop Effects", you can activate it both with a keybord shortcut (CTRL+F8 by default) and by navigating to a window corner, if you have set it up to do so in the "Screen Edges" menu (which you can find with KRunner).
From there you can select, add and remove workspaces.
If you go into settings > shortcuts > global shortcuts > kwin, and then search for desktop (only necessary to show only shortcuts related to desktop in kwin, and to have the change desktop options near the top of the list). You can then set up shortcuts for going one desktop to the left, right, up or down. So depending on how you have your desktops laid out, you can re-create the gnome shortcuts here.
As you do this, if you have the
Desktop Gird feature enabled, you will notice it here mixed in with all the other options. If you change the desktop grid shortcut the desktop effects, it will change the kwin shortcut as that is what it is using. You can also go to settings > desktop behavior > virtual desktops > switching (tab at the top) to change the desktop switching shortcuts at the bottom which, again, will actually change the kwin shortcut. All that means is that you can freely change the setting in either place to without any problems.
I usually have mine laid out in a single row, so I usually do left and right instead of up and down. you can also use next and previous desktop instead of left, right, up, and down.