The Delay effect module lets you apply a delay to the selected sound.
A copy of the selection is offset by the amount specified in the settings dialog, and is added to the existing selection.
The last part of the selection will fall out of the boundaries of the selection when offset. So, if in SoundEffects’ Preferences you choose to extend the effect to the outside of the selection too, this part will still be mixed to the following sound (or silence if there is no more sound), even if it’s out of the selection.