New version 0.0.6 available at the start of this thread.
As mentioned above:
Add / Fixed:
- when the option for subtitle is selected, the subtitle will be added to the title ( syntax: title: subtitle)
- for isbn the isbn13 format will be returned by the plugin
The indexnumber of the serie was already set to blank if that was not given by AdLibris. It is calibre itself that sets the index to number 1 in that case.
So cannot change that by the plugin, for it is unknown which serienumber are already used.
Thanks to RAHYA for testing so far and giving great feedback.

I think the plugin is good enough to be official annouced , so I will ask to serve it within calibre.
Please notify me in case of errors , website changes or requests.
Enjoy.