If you look at the .html file you will see that it is a document of sorts which contains the info of the clips you archived.
It along with the .xml and the folder of images house that.
It is really just a reference file for you, or if you are crafty enough to build/use a web dtabase of sorts they could be useful, but they are not needed for using the .seg files.
The .otoc file is still useful... maybe. Back in the day when you archived to tape, a header would get written in a sort of magical metadata noise frames. Obvious with tape, tape can get damaged and sometimes the header would get damaged and you would have no way to open the archive. The .otoc or Online Table Of Contents, allowed you to open your archive with a damaged header.
I suppose they are still useful for file archives... since they are small, you can leave them on your system or feel free to move them with the archive.
You can disable the HTML and otoc when you make the archive... there is a button toggle for it. Then these wont get made.
I have had only one file archive become unreadable. And I think it was user error on creation. Even the .otoc would not open it.
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