I'm slightly confused. A level editor, to me, is for creating game assets. No need to support events or any scripting. There are several around. Unless you meant in-game editors/hotkey activated. The torque engine was great for that but garage games is now defunct so it's future is uncertain.
The pipeline for Python/Panda3D is a 3d modelling app such as Blender or Maya. Create 3d level, export, load in script. Blender, like Panda, supports Python scripting.
Not that confusing, but my levels are pretty interactive. When you go up the stairs play that movie. When you talk to that guy get that weapon, when you go past that, a certain creature will jump on you. Just the basic things that keeps interactivity on. Maby something like, restore HP when you touch an orb.
Something like that can't be in an exported level if you made it in Maya or Max. So normally I have to program an additional file to go with the level. If the user is at location X,Y,Z do that.
So yea, I like my levels interactive, which makes a level editor with events pretty useful...