I have read most of the answers and one of the best things about a series timeline is that you can go into the timeline and move them up or down as needed. if you go into a series that you've started, there is a place If you go into any story of that series and look at the title page, you'll see the series name in a long rectangle, and to the right, there is a second rectangle with a mysterious symbol in it. Click on it, and all the members connected to the series will be listed in the order Lush has them, with arrows to move them up or down. This does not go to the moderator. you do need to check because i've seen stories with time lines all messed up
Second, when I've started a series and added names, I edit the story with a note to the moderator that all I've done is add the story to a series. It gets done very quickly for me.