UPDATE: I noticed in Edge Version 132.0.2957.140  that the panels are now resizable. WooHoo!

I am an Edge user, and recently, I have noticed that I can no longer resize the Dev Tools area. This is really annoying, and to make matters worse, it doesn’t seem to happen all the time. I finally figured it out. It uses the locked sizes when your browser window is in fullscreen mode on MacOS. You can resize the Dev Tools panel when you are not in full screen, and sometimes, the panel will remember where it was last.

This video shows the issue.

Update from Microsoft

Good news!! On Jan 13, 2025, you shared with us this feedback: 

Dev tools are locked in position and size when Edge is set to full screen

We want to let you know that we fixed an issue that’s related to this feedback in an upcoming update to Microsoft Edge.

Thank you for helping us make Microsoft Edge better than it was before. We can’t wait to hear what you think of next!