Next-gen projects use a parent/child hierarchy for the epic/task relationship. This is not the same as the "epic link" functionality used in classic projects. Avion would love to be able to make use if this, but unfortunately, the APIs are not currently available. In order to still provide next-gen users with a hierarchy, Avion uses issue linking in Jira to link epics and tasks. If the APIs become available in the future, we will assess the possibility of using the parent/child functionality. It's worth noting that because of this, we do not import existing parent/child relationships in next-gen projects either.