Blessing of Versatile Training (5e Blessing)
From D&D Wiki
Requirement: you should have changed subclass of one of your classes at least once.
Select one of your classes, in which you changed your archetype sometimes in your past; choose your current subclass in that class and one of the previous.
Over the course of short or long rest you can switch your current archetype features for features of your other chosen archetype, or vice-versa.