Adding lyrics extension line under two notes

Hi. I know how to remove a lyrics extension line by going to Engrave mode.
But what about the opposite: adding a lyrics extension line where it doesn’t automatically appear, especially when there are two notes for the same syllable? How do I do that?

LyricsExtensionLine

Double-click the existing lyric and press the space bar before abandoning Lyric mode.

I found that I needed to press the space bar twice.

Yes indeed. Thank you all.