My photo "Library" is not displayed on my photos screen. How do i get it back.

Here's one possibility-- there is this normally invisible arrow thing to the right of "Photos" at the top of the sidebar--it only appears when you hover over that spot, so how could anyone possibly even know it was there??

Anyway, click on that to hide or unhide the pre-built albums like Library and Recents.

Is that it?

You're not the first!