When updating and Organizational relationship if the person has a new Position the only option is to overwrite the existing position.

This means that if I started in a job in 1994 as a mail clerk and over the years I worked my way up into management and then became the CEO in 2017 the Organization relationship would still have me as being an employee of that company since 1994 but my position would show CEO. without extensive notes there is no way of knowing that I haven't actually been the CEO for over 20 years. 

Position      -     From      -   To

Mail Clerk  -  10/9/1994  - 30/6/2011

Manager    - 1/7/2011     - 31/21/2016

CEO          - 1/1/2017     - 

This will allow one Org relationship and a full history.