1. VOB stands for "Video Object" as defined in DVD specifications.  Although a vob file is also an MPEG file, it has additional data that a standard MPEG decoder will not understand,  e.g., the private data, which only a DVD decoder will understand.  Those data include information about the file offsets and time duration of all chapters included in the VOB file.  

2. Whenever a vob file is edited, some of those information will no longer be valid and may be discarded by the editor; and some other data ("user data" in the MPEG specs) which include the caption texts, will be preserved by the editor.  This is why that the editor does not have a VOB format for saving.

3. To write back the edited VOB files to a DVD disc for playback on a standard DVD player, you will need to go through another process called DVD authoring, which can be done using Womble's DVD Maker, or using another DVD authoring software.

4. Please note that for most of the DVD authoring tools, the MPEG files saved from the editor will be accepted without modifications.

5.In order to preserve the original chapters, you should import the VOB files from a commercial DVD disc by using a software tool such as the DVD Decrypter or the DVD SmartRipper. Since those free software are very efficient in reading a DVD disc, no slower than direct copying the VOB files from within the Windows file explorer, this work around does not incur any additional manual work, nor any loss of efficiency.

6. Since the editor is single file based, and since the DVD file system breaks one continuous movie stream into multiple 1 GB segments, this introduces video and audio discontinuities when loaded by the editor as consecutive clips. Those discontinuities may exhibit as loss of video for a maximum of one GOP (about half of a second) and as loss of audio for a maximum of two encoded sound frames (about 50 to 60 milliseconds). Worse still, this frequently destroys the original synchronization between video and audio. To work around this problem, it is always better to read the DVD disc into the computer as one single file by setting the "No splitting" option in a DVD reader.