Yes, you do have to pick the field. It is also a pretty good idea to make a copy of the library first, if worried, so you can “undo it” in a sense! If you are sure the field is something you never use, I would replace the field with the character Z maybe followed by a comma and a space at the beginning of the field so you don’t lose any information in the field and can always replace the Zcomma_space with nothing to get back where you were! (using the change text tool in reference drop-down I think)