We've made a few small, but significant improvements to our beta feature Messaging Holdbacks.
Warnings for unsupported SDK versions
Since Holdbacks require fairly recent SDK versions (iOS 1.4.1+ / Android 1.3.1+), you'll now see an alert in the Messaging Composer if your mobile apps haven't implemented a version of our SDK that supports Holdbacks.
You can now add a Holdback to an existing message
Originally, you could only add a Holdback before activating a message. Now, you'll see the option to create a Holdback for all messages, even if you've already published them.