Lyric line problems

You can’t, Leo, but that’s the nature of the beast. When you complete “blue”, Dorico has to find the next note in the target voice, and it moves the popover there, setting the duration of the previous lyric to the distance between the popover’s old and new position. If you subsequently add a note in that gap, I would expect the prevailing word/syllable to be sung on that note unless it’s explicitly countermanded by another lyric. And if you create another lyric on that note, the duration of the previous lyric is immediately updated as appropriate. So I don’t see a problem here.