I had a mission that was 6x3 but after we played it we figured 3x3 would work better.

Is there no way to resize the board?

Even if it smushed all the tokens around or even wiped the slate blank completely that would be better.

Then I wouldn't have to make a whole new mission of the same name and paste all the rules into it in order to have it be 3x3...

At the moment switching the board size after you created the mission is not supported.

I'm adding this to our feature list.

FFG Software Support

any way to resize the board to be a 4' by 4' or 6' by 6'?

maybe by grabbing one of the board edges and dragging to resize the thing?