I would like to have a button to add the selected related posts directly into the post content.
Why this? Well, this is really a great plugin, very useful for retrieving old content and bringing it back to life. It's been updated for a long time. But, with plugins, I am always afraid that they can be abandoned. I have decided that I can use stuff like plugins and custom shortcodes for bells and whistles, but they can't be the foundation of a blog, since I could be left in the cold when in case of abandonment.
In this case, let's say that something in WP core changes so much that Microkid can't update the plugin anymore. The related posts are kept in custom tables: if you erase the plugin, not only the feature, but also the work you've already done, is gone forever.
What I'm doing now by hand: select related posts, preview, copy the related post list, paste it into the content, deselect related posts.
But if there was a button to add the related posts to the contents of the post, it would be standard WP data and it would be safe forever.