Label, which has the same configuration in Magnolia 5 and in Magnolia 6, is not being displayed in the switchable field.

Magnolia 5.7.3 on the left side, Magnolia 6.0 and 6.1.3 on the right side: (label = youtube video id)

In the "Inspect" tool you can see that the label is mentioned there, so it is just not being displayed.

Configuration:
tabVideoConfiguration.xml