That's a super annoying macOS bug; I've definitely felt that pain.

While Macscope can't fix the underlying issue in macOS, this is a perfect use case for its "Scopes" feature. It's designed to solve exactly this kind of layout restoration problem.

Here’s how you can solve it with Macscope:

When you have all your windows arranged perfectly on your external monitor, open Macscope.

Multi-select all of those windows and save them as a new "Scope". You could name it something like "Work Setup".

The next time you reconnect your monitor and macOS scatters your windows, just open Macscope and activate your "Work Setup" Scope. It will move and arrange all of those windows back to their saved positions on your external monitor in one go.

So, it essentially gives you a one-click way to restore your entire workspace after that bug hits. Hope that helps!