KB User's Guide - Documents Tab - Link Doc
This document explains how the link doc function works in the KB
When creating KB content, it's ideal to avoid repeating content that has been published elsewhere or elaborated upon in other documents. One tool available to help avoid repetition is the KB Link doc feature. The KB Link doc feature allows you to link a KB document into other KB documents easily and effectively.
In order to use the link doc feature, select KB link doc 
from the plugins menu (custom tab on nav bar or 3 dots on the right side of the editor)
You will be presented with a pop-up, as seen in the image below:
The fields are:
- Type - What type of link you are using, KB Doc, News, or Topic
- KB ID Number - The ID of the document linked, not the URL, just the ID
- Open link in... - Open in the current window or in a new window or tab
If the ID number is valid, the name of the document will be displayed in green.
After filling these out, click Insert and the link will be placed at the cursor. The link text will be the name of the doc linked.