They haven't written much about it publicly. I found out about it from a mention on Twitter: https://twitter.com/WorkFlowy/status/1275205249549193223

There are barebones instructions on the settings page:

Link editor:

We've all been on the edge of our seats... and finally it has arrived - a magnificent popup for editing your links! To activate it, hover over any link and then click on the icon that will appear. If you're feeling keyboardish, hover over a link and hit Tab.

Mirror items:

This lets you mirror items, you can have a single node in multiple places, search for related options in the item menu to discover that

Cloning is discussed on the forum:

https://workflowy.zendesk.com/hc/en-us/community/posts/360068180652-Transclusion-Cloning-Embedding-is-here-

There's also a mention of plans for the link editor (and bi-directional linking) here:

https://workflowy.zendesk.com/hc/en-us/community/posts/360067774692-Bi-directional-linking

I'm not a part of this but there's a Slack channel where things like this are discussed. From the forum:

if you'd like to join the WorkFlowy Users Group on Slack (where we make early announcements of what we're up to and releasing for testing), please shoot me an email at help@workflowy.com :-)

~Frank