Feature summary (what you would like to be able to do and where):
Automatically replace external URL:s with wiki links in the "Add a link" dialogue.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
In Visual Editor, it would be helpful if you could add links to (other) wikis by entering the full URL. I often copy-paste links to other wikis. In these cases I prefer to have a wiki link rather than an external link (not sure exactly what differences there are between the links, but since wiki links are a thing there must be some benefits🙂). This has to be done manually by replacing the first part of the URL with wiki link synatx, e.g. https://en.wikipedia.org/wiki/Monkey -> w:en:Monkey. As with all manual work, this takes extra time and prone to errors (e.g. remembering what prefixes different wikis have).

A top-of-my-head solution would be to do a simple when the user clicks on the "Wikimedia" tab in the "Add a link" dialogue, if the URL matches a known wiki.

Benefits (why should this be implemented?):
This would streamline the workflow when linking between wikis and would reduce the amount of incorrect links being added.