Can't find the editor?

1: make a shortcut, whatever.
2: mention it to anything.
3: copy this text:
"C:\Program Files\Unreal Tournament 3\Binaries\UT3.exe" editor

On the shortcut:

Right-click --> Properties.

Shortcut

In target box paste there. and OK
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If you have a modern PC, they tend to be a "Game Eplorer"
Right click on the Unreal Tournament 3 and Editor, pressure to start it.