Yeah for some reason, by default, this is like a hidden folder in Finder. Here is how to get it in your side bar:

1) Open Finder

2) Click , Go > Go To Folder, enter in the full path to the ~/Library directory

3) It should open in Finder. Now, drag the blue folder icon in the title bar and place it anywhere you’d like in the sidebar.

4) Done.!

More ways here.

Mario Loria is a builder of diverse infrastructure with modern workloads on both bare-metal and cloud platforms. He's traversed roles in system administration, network engineering, and DevOps. You can learn more about him here.