How can I add a link to another element within the same topic?

You can use the Link icon and manually edit the attributes to insert a link to another element.

Description

I want to link to another element within the same topic.

Solution

Perform the following to insert a link to another element.
Note: This solution requires DITA 1.3 and a 2.x OT.
  1. Add an ID to the element you want to link to. For example, 
    <p  id="link-para">
  2. Place your cursor where you want to insert the link.
  3. In the Oxygen editor, click Link icon.
  4. Click Cross Reference.
  5. In the Location drop-down list, select the current topic.
  6. In the Select the target element section, select the ID to link to.
  7. Click Insert and close. The xref is inserted as 
    <xref href="#hqm1517240717943/link-para" format="dita"/>
  8. Right-click the xref element.
  9. Click Edit Attributes.
  10. Edit the href attribute to remove the topic ID and replace it with a period:
    <xref href="#./link-para" format="dita"/>