Until a few weeks ago, there was a menu item "Accountant > Upload Documents". It's no longer there. How do I upload documents to my bookkeeper as before?

Welcome to the Community, @swift1. I'm with you in getting past on this issue. 

QuickBooks Online may experience unexpected behavior if the browser is holding too much data from previous browsing sessions. 

We can perform troubleshooting steps so you can upload your file for your bookkeeper. If you're not seeing the Upload a document link anymore, you can ask your accountant to create a request. 

Though, you can log in to QuickBooks Online using a private or an incognito window. Here's how: 

• Google Chrome: press Ctrl + Shift + N.
• Mozilla Firefox: press Ctrl + Shift + P.
• Internet Explorer: press Ctrl + Shift + P.
• Safari: press Command + Shift + N.

If that works, go back to your default browser to clear the cache or delete your temporary internet files. 

If the issue persists, I'd recommend using another browser. Here's an article for your reference: System requirements for QuickBooks Online, Accountant, and QuickBooks Self-Employed.

You'll also want to invite your accountant to view and manage your company files. Read through this article for more details and instructions: Invite or remove an accountant.

Let me know if you have other questions. I'm always around to help. 

I had previously tried clearing the browser cache (Chrome, on Windows 10) to no avail. 

With the help of QB support, they pointed out that the upload functionality is also accessible from the upper right link My Experts (an icon that looks like a person) > Accounting Pros > View Now.

From there you can see the Shared Documents and Document request pages.