Andrew Nacin

In WordPress 3.5, the Link Manager (which some use to build blogrolls) will 
be disabled by default. If you have links when you update, it’ll still be there. 
But you can use this plugin to ensure it will always be there, even if you 
update to a later version of WordPress or remove all of your current links.

Link Manager

Works on WP 6.1

Enables the Link Manager that existed in WordPress until version 3.5.

tunaucom

Display all bookmarks (link manager) in your WordPress login page.

TNC Display Bookmark In WP-Login Page

Display all bookmarks (link manager) in your WordPress login page.

Link Manager vs TNC Display Bookmark In WP-Login Page