"edit the content on the dvd with editing software."
No editor today can edit the content "on the dvd". We can use the dvd content as source material but no editor known does direct editing of the DVD. Sorry but just English at play here.
Demos of such software is plentiful. Try Video ReDo and others.
Can I record from a older handycam to a dvd recorder, then insert the dvd into the dvd drive in the computer and edit the content on the dvd with editing software. Any help would be appreciated