OneDrive needs the ability to search individual folders. "Search everything" is useless if you are search if you have 10000 results.
Why can't you search an individual folder. I'm looking for "text123", and I KNOW it's in a folder 5 subfolders down. But above that subfolder, "text123" yields 800 results. If I could search the subfolder, it would yield the 1 result I needed. So your search everything is useless, because I'm still going through 800 results.