Hi Pat, I don't work for Roxio but I'll try and help as much as I can.
1- You'll need to do this ALL in NEW LAYOUT and I seem to remember where I was able to add a video by dragging it to the left of the little menu icon. I haven't really played with this feature but when I do, I'll post about it. (Just Tried it.. DIDN"T WORK)
2- The video thumbnails will play the video that is for that added file. I'm not sure what you're looking for on this one. As for removing text, have you selected it and then hit the delete key? I don't know if that will work either (DIDN"T WORK EITHER). I've posted plenty of "pissed off owners of Corel Roxio Toast" but please remember, this is the first version they have released with custom menus and I'm sure they won't put it thru the paces like the users will.
3- As for subtitles, additional audio etc, you're looking for features that used to exist in DVD Studio from Apple and other higher end programs. If these capabilities exist, I haven't found them yet but then again, I only got the program upgrade yesterday.