Is there an option to edit title-parameter for Links in Redactor?
There's currently no out-of-the-box way with Redactor, other than to open the HTML source view and adjust the &lt;a&gt; tag manually to be something like &lt;a href="yourlink" title="yourtitle"&gt;.

All Redactor settings regarding links can be found here: http://imperavi.com/redactor/docs/settings/links/