Opening edge length is the perimeter of the opening measured in linear feet (LF).It is not replacing opening area, but currently, opening area cannot be represented or included in a component, only in the root wall.
This is different from how it worked in v16, but I’ve added it to the feature update list right away, since including opening area in components is important for estimating.
As a workaround for now, please create an assembly on the root wall that subtracts the opening area for plywood/sheathing.