If you want to be able to randomly remove things from a disc there are two ways to do it…
Copy everything to an empty harddrive, edit what you want to edit erase the entire disc and burn it again.
the other way is to use a DVD-RAM disc which WILL allow you to do what you are describing.
Frankly I wouldn’t back anything up to a DVD-RW, because the
amorphous pits gradually revert to their native crystalline state effectively erasing your data over time.
THe use for a DVD-RW is to verify that you are burning it “correctly” before using a “write once” disc to do the same job.
But burned optical discs are never as good as a safe storage media for backing up important data to another harddrive that you DISCONNECT after making your copy.