In the text field "Description" you can insert links in the following way:
Mark the desired location in the text with the mouse and click on the (chain symbol) above the window in the editing window; this opens a small link-window, into which you can enter the target link. According to memory the selected text will appear as the clickable link
The specification of the complete URL in the descriptive text is also possible. http://www.mylink.com then becomes: www.mylink.com
In this way you are able to link different image series, case examples and documentation on the progression of cases with each other or make reference to websites with further information on the topic.