Career progression
After a controller is endorsed for a unit, further steps are set by that employer. There is no single ladder used worldwide.
Moving to another unit, or from tower work to approach or area, usually means more training and a new endorsement. Time spent at one airport does not by itself qualify someone for a centre.
Some employers also appoint controllers as instructors, examiners, or supervisors. The titles, and the path to them, are local. When this site describes a path at one employer, it will name the source and the year.
The first qualification is covered under Training and Licensing.