@webe - do you mean you are putting different custom text on each book?
There is no way for this plugin to know what text you used previously on a particular book currently. If you have a different custom text for different types of books (e.g. fantasy vs scifi or whatever) then you can create a different saved setting profile for each, and then quickly switch to that manually when you open the generate cover dialog. That is something you can do with the current released version. Of course it doesn't have to be genre specific - you could have a saved setting just for variations of your custom text. However that is the best I can suggest with what is there today.
An option I guess I "could" do in a future version is to save all your settings at the time you do generate cover into the book plugin data in the database. So a bit like when you do conversions, it would remember all the settings you used when you last generated the cover for that book as a default. That would save you the steps of manually selecting from your saved "default" profiles and restoring any custom settings you had done specifically for that book.
However that has complications of its own. What if you select multiple books, that were previously generated with conflicting settings? I think it could all get rather confusing. You get a similar situation that bulk conversion does of asking you whether to use the saved settings or the current values. So the UI becomes more complex. And you have the issues of stuff like what if you no longer have the image file used etc.
I'm not going to add extra stuff to the database/UI if it is the kind of thing you only need once in a blue moon as it is a fair amount of work. I find in my own usage that with a set of "default" saved settings I am happy just to have one click to override the "last settings" with choosing a saved setting in the situation of regenerating a cover. It doesn't happen often enough to have a need myself - I make sure my metadata is correct before I generate, and unless I decided I wanted to apply a new cover image/style to a whole bunch of books (in which case a saved profile will be what I want anyways) I don't need to revisit it.