Google is testing adding search refinement options in the sponsored ads in a carousel format. The test shows refinements named "fine-tune your search," "search specific products" and "specify your search." But I bet there are more.
This was spotted by Sachin Patel who posted three screenshots on X - here they are:
Sachin wrote, "Google replaced 'Refine your search' with more headings." Anthony Higman replied, "Have not seen in that carousel format!"
Forum discussion at X.