SUMMARY
In a multi activities setup it would make sense to be able to use hotkeys to switch to another activity as well as move a window to another activity, much like Switch to Desktop.. , Switch to Screen .., Window to Desktop .. and Window to Screen ..

STEPS TO REPRODUCE
1. Open Global Keyboard Shortcuts
2. Search for shortcut to switch to activity
3. Search for shortcut to move window to activity

OBSERVED RESULT
No Actions exist to either switch to or move window to activity.

EXPECTED RESULT
There should be actions to allow switching and moving window to another activity.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSuse Leap 15.1
KDE Plasma Version: 5.12.8
KDE Frameworks Version: 5.55.0
Qt Version: 5.9.7

ADDITIONAL INFORMATION
There exists org.kde.ActivityManager/ActivityManager/Activities DBUS message which allows switching to another activity via SetCurrentActivity but 
dbus-monitor does not record any dbus message when moving window, so I guess there is not a DBUS message to use a custom shortcut.

PS. Maybe for a home user, saving 2-3sec when switching/moving around windows doesn't make any difference but in a business environment with 10 activities x 4 desktops each, used all day long, it would be a notable timesaver.