Thanks Jane,
You answered the question I raised.
I didn't explain myself too well.
What I was seeking was a simple way to change a bookmark rather than delete it and then add a new bookmark. I was hoping for a quicker route than that because at the back of my mind is that fact that I'm cataloguing my books at the moment according to where they are located in the house and then I plan to regroup them according to content, e.g. ethnicity and I was hoping to open the list of bookmarks and then edit them...
However, on reflection, I realise I should add the content bookmarks now and when I want to relocate them together according to content, I can call them up by content bookmark and it will help me calculate the space required.
Sorry for waffling on... I've got it now. Doh!
Best wishes from a woman of a certain age with over 1000 cookery books to catalogue but thank heavens I now have a tool I can do it with.