Fahmi Adib

If activated, this plugin will strip all links from your post/page before the date that you set

WP Scheduled Links

Schedule when link(s) should appear on your post/page

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.

WP Scheduled Links vs Link Manager