Typing or holding down the backspace key to remove existing text from the search field in your creative inventory isn't always responsive. I'm using the "Classic" UI Profile.
Steps to reproduce
Make sure you're using the "Classic" UI Profile.
Search for an item in your creative inventory. (Text you type doesn't always appear right away.)
Hold down backspace key to erase name of item. (The text you're removing isn't being removed very quickly. There is always a short delay.)
@unknown: Does this get gradually worse the more you use the search function?