gnomebaker multisession

Hi I new to this app. I can't find how to multisession within gnomebaker. I put in a dvdrw that had some data on it and it erased the previous data that was on it and I don't want to make that mistake again. The previous data was burnt with k3b when I had debian installed and was a multisession disk so I am really dissapointed that a lot of data was lost. Gnomebaker didn't ask before erasing the data which k3b does. Anyway I have searched around on the net and also cannot see any info.