The Open Sequence button opens a Video Post sequence stored on disk.
Video Post sequences (VPX files) contain all the information relating to the queue and all associated settings and references.
To open an existing Video Post file:
Use the file selection dialog that appears to choose the VPX file you want to execute or edit.
To import an existing Video Post sequence:
You can also use Open Sequence to import the Video Post queue from a 3ds Max scene (MAX file).
Video Post loads only the Video Post data from the existing .max file, leaving your current scene unchanged.