Yes, the left panel has been pinnable and resizable for some time, and I love it: if you have a small monitor you unpin it, if you have a large monitor you pin it.
For some reason they now decided that when the app is running, I can’t pin it any longer.
I don’t understand why.
It was already possible to unpin it if you wanted to, and it was possible to keep it pinned. Now you can’t. I don’t understand where is the added value of removing a very useful feature.
I work with a 4K 40" monitor, 3840x2160 and unpinning the left panel is just wrong.