I hope you're doing well, Alan.

Yes, there's a way on how you can check the list size in QuickBooks Desktop. All you have to do is press the F2 key or Ctrl+1 on your keyboard. Then, review the List Information section or the File Size in the File Information section of the Product Information window.

Here's a sample screenshot for a visual reference:

To learn more about the file limits, you can read this article: Maximum number of list entries (list limits and custom fields).

If you need anything else, please let me know in the comments below. I'd be glad to help you out again. Stay safe!