What do you mean library? The address bar?

Yes it was in the the Library Icon on the toolbar

Unfortunately, this option has been removed in the recent update. Now, to see your list, you have to go to https://getpocket.com/my-list

Sorry, for some reason, you now need to access it like any other site and either enter the address in the address bar or set a bookmark for it. The URL is:

https://getpocket.com/my-list

Ref. Save web pages for later with Pocket for Firefox

See also the release notes.

• https://www.mozilla.org/en-US/firefox/87.0/releasenotes/

We've removed items from the Library menu that weren't used often or have other access points in the browser: Synced tabs, Recent highlights, and Pocket list.

• bug 1689405 - Do initial simplification of the Library menu

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Thank you ALL