I found a way to fix this for those who use the Left Icon Bar!

After the last QuickBooks update, a redundant and annoying top search bar appeared for me and I could not get rid of it. I tried removing it under Edit > Preferences and under View, but the options to remove it were grayed out (not clickable).

However, I discovered that if you go to View and switch to Top Icon Bar, the options to remove that search bar become available! You can then open the View menu again and uncheck "Search Box". This will get rid of the annoying top search bar. Finally, go back to View and switch back to Left Icon Bar, and the search box will still be gone. Hope this helps!