You can add a gap or delay in your script by adding (gap: Xs) in brackets and mentioning the number of seconds you want the voiceover to be delayed.

As shown in the screenshot, you can manually add (gap) between chapters from the edit script section.

You can remove the gap from the video via the Magic box:

Or if you have a pause with the duration mentioned, you can use this command:

You can add a gap between lines/chapters if you want only the media with the music to be playing.

You can add new lines between sentences as shown here.

Note: You have the option to change the speed of the voiceover now as shown here.