not with DVDstripper
if it was a movie only DVD then it's simple but if you want to keep Menu's, angles etc then things get confusing
it's not impossible but it's hard to do even for the more experienced. I did it once after splitting a DVDStripper DVD and it could be automated to make it a real simple process but that's upto TMG to implement and when I don't know. I am yet to see a reply to this question that actually tells you how to do it without having to completely reauthor the DVD using authoring software to try to maintain the original workings of the DVD
it will all depend on the original structure and how the DVD was split and I know you have used DVDFab and although I'm not 100% sure, I don't think you can join them as easily as splitting
p.s. hope you saw my post regarding which version of DVDFab you are using and how you are doing it, with what options