Listbuilder advice

Hi all - looking for advice from anyone who uses the listbuilder app to collect email addresses, particularly when offline. Have you had success syncing these contacts into your account? How are you keeping track of contacts collected via listbuilder? After a chat with support it's clear the functionality is quite limited, but I'm wondering if anyone has been able to make it work for their organization. I'm mostly worried we are losing contacts collected when offline. Thanks in advance for any info/advice!