Bob,
Glad it helped some. I'm not sure if I am understanding the part about the not deleting but see if this helps.
When you choose the part of the video you want, then go to your save as area in the program you are using, Always you "save as" if it's like my program or you will erase everything else LOL.
Anyway click "save as" after you have chosen the portion of video you want, then give it a name, I usually give mine a name such as 3d routine 1, then the next segment do the same thing pick it out then "save as" again ex. 3d routine 2.
The reason I name them that way is so I know in what order I want to reassemble the portions, and the main name tells me what it is in case I'm working on something else.
LOL Plus getting older and my memory isn't as good as it used to be LOL

Hope that helps,
Jim