Trigger Unlock conditions allow you to unlock your action. Before reading this article, you should read about Trigger Conditions.
Each time a Trigger Condition is met, the trigger is locked if there is at least one Trigger Unlock condition.
If the Trigger Conditions are met but there are no Trigger Unlock conditions, the action won't get Locked.
When an action is locked, it will never get triggered. You can check if your action is locked by looking in the Locked switch, just like the screenshot above. If the Locked is gray, it means your Action is unlocked, if it's red, it means your action is Locked.
You can also set this Locked parameter manually, all you have to do is click it to toggle between Locked or not, and then hit Save.
Why does this exist?
One example of an undesirable situation could occur when you want to receive only one SMS when the temperature crosses above 95 C, but instead you receive one SMS for each time a new value of temperature above 95 C is sent (95 C, 96 C, 97 C).
You may want to implement a hysteresis using a Trigger Unlock condition. If you define the condition to reset when temperature is Less than 90 C for example, it would prevent this issue.
Only one SMS would be sent, and the system would be locked until the temperature goes below 90 C. Which seems much more reasonable in this example.