How to change absence plan accural to person, instead of assigment

Summary:

We have multiple assigments, when one ends, another when will be active
We want to have absence accural attached to person, noget assigment

On create a new absence plan, i can only see the option to have processing level to assigment, how to change it to person?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):