Is there a quick way to send windows to another activity? At the moment, the only way I can see to do this is by right-clicking the menubar (or pressing Alt-F3) then selecting the "Activities" submenu, and selecting within there. The only problem is that this is checkbox-based, not radio button based, so I have to do this two times just to send the window to an activity. That is, I have to select the destination activity, then I have to deselect the original activity. This makes a sum total of six actions.

In comparison, I can send windows to another desktop in one action, by using a keyboard shortcut (System Settings > Global Keyboard Shortcuts > KWin > Window to Desktop 1). e.g. send the current window to desktop 1 by pressing Meta+Shift+1.

I think this needs to be implemented in the global shortcuts for the activity manager daemon. Please file a wishlist bug on bugs.kde.org.

Thanks. I've filed a bug here.