Unless I’m missing something (entirely possible), you can no longer select a post from a list of older content by using the link options when you create or edit a link in the new WordPress editor. You can only search for the content, and if you can’t find it, well, you’d better open another browser window and prepare to hunt it down and get the link that way.
What the hell, WordPress?
The old way to add a link
The new way to add a link
If you’ll notice, the options bring up only the option to open the link in a new tab. You no longer get that helpful list of recent posts.
Blah. Just another way WordPress has degraded on the usability front. I’m just so disappointed with this new version that I’m seriously considering a change back to static HTML websites for the first time in years.