@ V@no.
I think he meant to put once descriptions and keywords for every category , for example I have Santa Teresa Gallura pictures which is the city on Sardinia (Italy) , I have 800 pics in this 1 category , I think that he meant to make once keywords (Santa Teresa Gallura , Sardinia , Sardegna , porto , cità , etc) and description (Santa Teresa Gallura is the small city on....) So one description and keywords for all pictures in each category batching these keywords in all 800 pics at once - with batch Copy /Edit /Move he has to go everytime to Copy and Insert these keywords and description in each image separately . This would be a very useful Mod to make it once - not 800x. And then with Mod Batch Copy/Edit... to repair some keywords of images - (add - delete)
@Peaces
If you are searching for this as I described above I don't think that you will find it here yet , I was searching for the same and till now didn't find it