This is how I achieved it.
First, duplicate the Total Hours metric.
Second, drag it to the Measure Values card right after AGG(Total Hours).
Third, right-click on the newly added measure and choose Quick Table Calculation - Percent of Total.
Fourth, change the alias of the new column as you like.
This gets you what you described. There is a bit of magic here - I don't understand why I wasn't able to achieve it on the original column, but I got it on the copy. Possibly due to definitions in other sheets or dashboards.
Hope this helps. Don't hesitate to ask if you have further questions.
Call Labor Report v8.twbx 9.6 MB
That worked! Thanks for the help