Linking Issues - Not Possible to Select Multiple Issues

Steps to Reproduce:

1. View the issue from which you want to create a link.
2. On the 'view issue' page, select Link from the More Actions menu or if available, click the Add Link (plus) icon at the right of the Issue Links section.
3. Click on the 'search for an issue' link.

Expected Results:
To be able to select multiple issues, by clicking the 'Select multiple issues' link. Checkboxes would appear, enabling multiple issues to be selected.

Actual Results:
It is not possible to select multiple issues when searching for the issues(screenshot below), which was possible in JIRA 5.0 (screenshot above) and previous versions.

Workaround:

1. Search for the issues using the issue navigator and export them for Excel;
2. Open the file and select all the issue keys under the Key column;
3. Paste it into a text editor (e.g. notepad, notepad ++, etc.); select and copy all the issue keys (which will be displayed one in each line)
4. Paste it into the Issue field when linking the issues and click outside the field so all keys will be rendered.
   ^{Reference from Atlassian Answers}