When a trigger that has a URL enters a problem state and appears in the 'Last 20 issues' section of the dashboard, the trigger name in the 'Issue' column becomes a link to that URL. Currently that link will open in the same window/tab as the Zabbix dashboard, unless the user asks their browser to do otherwise (e.g. using 'Open in New Tab' from the contextual menu).

I'd expect that many users would want to keep the Dashboard open at all times, so having this link open in a new tab by default (using target="_blank" or similar) might prevent them from accidentally loosing their Dashboard tab/window. Of course this could be made configurable on a site-wide or user-specific basis if thought necessary.