Hi Daniele,
The Preview Dialing doesn't have a redial button. If you really want to have an option to dial the same number a second time, you would have to add an extra column in your contact list and tweak your translation rules.
The agents will see something similar to the below pictures. If a call to the first number gets disconnected the agent can dial the second number, which is the same number with 0 in front.
For the scenario where the customer didn't answer, you can reschedule a callback to one hour later or to the next day. This is not the best solution but it's the only one that I know.
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Paulo Mesquita
Spark NZ Trading
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