I'm thinking of making a video editing event
Where should I put it? I mean, the design events board doesn't seem the right place since all it's used for (from the looks of it) is when you're looking for replays.

It does go in the design events board.
Most people use it for replays because it's simpler to keep it selected there.
It was originally made for things like mod creation, videos and stuff.
The Urban vid contest and ishi's farm mod contest were posted there.