Studio makes it easy to split segments. You can split basically any segment — just right-click the desired split location and select Split Segment. Similarly, you can join segments by selecting the segments by clicking the segment numbers while keeping Ctrl button pressed and then selecting Merge Segments from the right-click menu. Nice and easy.
However, what’s not nice at all is the fact that you can’t join segments that are separated by a hard return in the original file. So, if there’s a hard return in the middle of a sentence (because of poor formatting) you are stuck with it and have to translate the sentence as segmented (or fix it in the source file and then retranslate the file from the beginning). Very frustrating. In Trados 2007, you can easily delete the erroneous hard return symbol from the text and then open the segment again for translation. This is definitely an item for my Trados Wish List!