How come does the 'edit-links' command remain grey no matter what I do? Can
it really be that it's not available? Is there some update available
somewhere?

I've already tried the alt-F9 so that I could change the name of the source
document, but this only shows the end part of the link's name, and so the
find-replace command doesn't find the name of the source.

What to do? Changing all the zillion links manually looks like a tedious
job...