I personally find it tough to properly time animated effects in the level editor, so make it so that if you add an animated effect, a line will follow that represents how long the effect will last, and the line can be resized to adjust duration, and also make it snap to the current beat snapping setting, or not snap it at all. An ability to add difficulties and assign and resize very big images to difficulties in the level editor would also be useful, now that you can swap difficulties in the level editor.