Yes it is possible, but there is a trick: The series information doesn't get sent when you first send the book to the device. After the book has been processed and is in the device's library, you need to re-connect the device to Calibre again and the series information will be sent then. You also need to check that these two options are set in calibre:
Preferences > Sending books to device > Metadata management: Automatic
Preferences > Plugins > Device interface plugins > KoboTouch > Customise plugin > Set Series information: Tick
Edit: This is optional, most people will not want to bother, but ... Calibre has a limitation in that its series index can only be a number. It is possible to get around this by editing the device's database, setting the series information manually to anything you want, but in that case you would want to untick the KoboTouch driver's Set series information option to prevent it overwriting the manually set information. In the screenshot below I set the series index for the last book to 3,4 with the sqlite3 command:
Code:
UPDATE content SET Series='Kencyrath', SeriesNumber='3,4' WHERE BookID IS NULL AND IsDownloaded=='true' AND Title=="Seeker's Bane";