Here is the correct display of the Item Pane when pinning the "Libraries and Collections" section:

https://s3.amazonaws.com/zotero.org/images/forums/u265723/x7pwh8luewhw7p4c9vff.png

Here is what it looks like after switching in the Items Tree from a note:

https://s3.amazonaws.com/zotero.org/images/forums/u265723/kqfu6w9yjbxa1vt21k0v.png

Zotero 7.0.0-beta.91+3c6625f3c (64-bit)
Windows 10