In the Notation Window, when I'm entering lyrics, by clicking on the L button, I would like to move back and forth, using left and right arrow keys, allowing me to fix some mistyped lyrics.

By the way thank you PGMusic for the great feature that allows me to type the lyrics while listening to the notes. I've never seen this feature in any other DAW! This feature turns my job a lot easier.

when you are entering lyrics using the L button, <enter> moves you to the next lyric, and <shift-tab> moves you backwards. Actually, I think it moves you to the next note, so the might be an issue if you have deleted a note that had an attached lyric event. Best to use the event editor, the <#> button and click the lyrics tab.

Thank you very much Dave, I didn't know about the <shift-tab> to go back.

About the Lyrics Editor, it is so difficult to edit the lyrics!

Kinda - but knowing how to move forward and back can help. But lyrics editor can be very useful as well. You can actually move a lyric event as well with the editor using the actual event position.