Step 3: Defect? De-Effect

Movie has Undo, but it's sequential. So if you add an effect and then make 30 other changes to the project, you'd have to hit Command-Z (Edit > Undo) 30 times to undo that effect, then reapply the other 30 changes. Plan B: iMovie stacks effects on clips in the order that you apply them, so if you apply Rain, then Lens Flare, then Electricity, and then you decide the Lens Flare needs more adjustment, you have to remove the Electricity effect; then remove, adjust, and reapply the Lens Flare; then reapply Electricity. Click a clip's thumbnail in the Timeline's Clip view and press Delete to remove the most recently applied filter. Press Delete again to remove another, and so on. If you're hyperorganized, make a list of which filters you've applied to which clips-otherwise there's no way to know which one came first.

The number 8 means we've piled eight effects onto this scene.