Zoom the screen with Alt+Scroll in KDE

Install xbindkeys, qdbus.

Enable KWin zoom effect. For best experience, lower the zoom multiplier.

Add this to .xbindkeysrc in your home folder (or create the file):

~/.xbindkeysrc"qdbus org.kde.kglobalaccel /component/kwin invokeShortcut view_zoom_in"
    alt + b:4
"qdbus org.kde.kglobalaccel /component/kwin invokeShortcut view_zoom_out"
    alt + b:5

It is possible that qdbus is available under a different name, like qdbus-qt4. Try the command itself (without quotes) and see if it has any effect.

Alternatively, with dbus-send:

~/.xbindkeysrc"dbus-send --type=method_call --dest=org.kde.kglobalaccel /component/kwin org.kde.kglobalaccel.Component.invokeShortcut string:view_zoom_in"
    alt + b:4
"dbus-send --type=method_call --dest=org.kde.kglobalaccel /component/kwin org.kde.kglobalaccel.Component.invokeShortcut string:view_zoom_out"
    alt + b:5

You may want a different modifier. For Meta/Super key, replace alt with m:0x50 + c:133.

Then activate xbindkeys:

killall xbindkeys
xbindkeys

Add xbindkeys to startup.

References:

• Mouse shortcuts with xbindkeys
• Desktop Zoom in KDE using dbus-send