The upgrade documentation states you should backup any custom action packs
How can we backup custom action packs?
Release : 6.4, 6.5, 6.6, 6.7
Component : CA RELEASE AUTOMATION RELEASE OPERATIONS CENTER
All action packs are stored in the actionslib folder, for example:
You should be able to review through and pull the JAR(s) for custom actions from that location in preparation to reload after the upgrade or in a new environment.
Regarding the upgrade itself, please be aware that the recommended upgrade path is 6.4 -> 6.6 -> 6.7.
See KB https://knowledge.broadcom.com/external/article/189829 for details.