For v1 hub:
There is no z-wave exclusion available through the new app. You need to use IDE.
For v2 or newer hubs:
Go to the Devices section, click on the home icon in the upper left of the screen, find All Devices in that menu, find your new hub and open it! Click on the three dots in the upper right of the screen and select z-wave utilities.
update: this is an old thread with outdated info. current z-wave exclusion is available when you open the tile for the hub in the ST app, tap 3 dots and choose Settings and z-wave utilities.