Writeable and read-only documents

[PJMiller]

Having imported some documents into Ultra Recall I notice that I cannot edit them, they are text files but even thought I have set the extension (.gvz) to be writeable in Tools|Options|Documents|File extensions to open stored documents writeable:

I also noticed that some of the other files I have imported (.txt) are also not editable.

What am I missing here?

How can I edit these documents?