There is no official Tableau Desktop connector built in Tagetik.
For a full list of supported data sources, are available on Tableau website.
You can post in our Ideas section in order to get it implemented. The more votes you got the better chances you have to see it implemented.
A possible workaround option is to use the Web Data Connector in order to connect to Tagetik.
The Web Data Connector option provides a way for Tableau Desktop to connect to data that doesn't already have a connection option in Tableau Desktop.
For more information have a look to Web Data connector documentation below.
Hope this help.