Lyric line numbers are used to organize lyrics when a single musical passage can have different lyrics sung to it, such as music that contains multiple verses. In Dorico Elements, you can specify the line number of lyrics as you input them and by changing the line number of existing lyrics.
In Dorico Elements, you can have multiple lines of lyrics both above and below the same staff. Turning lyric lines into chorus lyric lines or lyric line translations changes both their placement and appearance as chorus lyrics generally use an italic font.
Lyric lines always appear in numerical order, both above and below the staff.