Tracking leader stats - Most on_actions now track a leader's progress, setting flags or incrementing a stat based on what occurred: Pop grew, colony lost, war ended, ship destroyed, tech researched, etc. Leaders that live long enough can gain achievements, such as: claimed many new systems, researched many anomalies, purged many species, or lost many ships. Unique circumstances may also cause the leader to become infamous, such as allowing rebels to take over a planet, or allowing pops to die due to overpopulation.
View living leader stats - You can view your current leader roster's stats and achievements via an edict that iterates through them.
Honor leader upon death - Upon a leader dying, a dialog will show that shows their stats and achievements, and gives you three options:
Honor them at cost of some influence, which gives unity based on leader skill, and a 10 year country bonus based on the leader's traits and achievements. It will also rename a set of objects: system,planet,army,ship etc. based on the leader class.
Save them for honoring later - currently can save up to 5 leaders of each class for a total of 25
Ignore them and they will be gone forever
View Saved leaders and honor/delete them - You can view the memorialized leaders via another edict, and honor them again for the cost of influence, or delete the ones not worthy of further remembrance. If you wish, you can also honor a historical leader, which is randomly generated.
Construct Memorials - Megastructures built in orbit of a planet that permanently provide unity and a bonus based on the leader class, as well as traits and achievements from the memorialized leader.