The button should open the same url that the user is currently browsing in the page editor. Currently it opens the path to the current page, which can result the wrong content being displayed because it does not take into account the mappings, the selectors (ie ~), or the querystring.

Due to this problem, a different, or broken page is sometimes opened when using this feature.
Additionally, part of the need for this feature is that developers and authors can work with and see the actual url.

Examples from the travel demo:

Navigate to any specific tour in the preview mode of the page editor. for example click on the Malasia tour in the carousel.
Use the Open-in-tab button.
Expected: the Malasia tour is opened. URL is /tours/magnolia-travels/A-Taste-of-Malaysia.html?mgnlChannel=desktop&mgnlPreview=true
Actual: the Switzerland tour is opened: URL is /travel/tour.html

Navigate to any tourtype category in the preview mode of the page editor, for example "cultural".
use the Open-in-tab button.
Expected: The Cultural tourtype page is opened: /travel/tour-type~cultural~.html?mgnlChannel=desktop&mgnlPreview=true
Actual: The Active tourtype is opened. URL is /travel/tour-type.html

Navigate to any destination category in the preview mode of the page editor, for example "Central and South America".
use the Open-in-tab button.
Expected: The "Central and South America" destination page is opened: /travel/destination~southAmerica~.html?mgnlChannel=desktop&mgnlPreview=true
Actual: The Active tourtype is opened, but somehow broken. URL is /travel/destination.html

Notes
See comments from https://jira.magnolia-cms.com/browse/PAGES-73 for images and some discussion.

It would be preferable to remove the mgnlChannel=desktop&mgnlPreview=true string which is appended by the editor.