Rynus_Rein has kindly enough created a program to add series and chapters to KiwiComics.
Actually, I wrote a little .NET application (should also work using Mono) which allows you to add series/chapters/pages to the sqlite database which is used by KiwiComics.
Basically you download the .sqlite file from your iPhone using SSH, add new chapters/pages and upload it again.
The application is not very user-friendly since I’m the only one using it, but would anyone be interested in this too (then I would polish it and upload it somewhere)?
Write your thoughts and/or support in the comments. You can find his homepage here.