If you configured Next-Best-Action Designer in versions earlier than 8.5, you can continue to use the legacy configuration. However, to benefit from the new features, update your next-best-action configuration.
Pega Customer Decision Hub Update Guide
You can upgrade the Next-Best-Action Designer at any point after you upgrade to Pega Customer Decision Hub 8.5. For more information about the process, see Upgrading the Next-Best-Action Designer.