Sorry, I figured this out. If I want to use the layouts plugin, I have to use child layouts. However, as a side note, this is a bit restrictive, in that one can only specify one child layout cell per layout. So, in this scenario, I can only make the content area a child cell, and the sidebar becomes fixed.
This means that if I want to have two variations of a complex content area, each with its own distinctive sidebar, I have to make two parent layouts, using the child layout capability to address the content area only.
From a global design standpoint, where layouts should be hierarchical, this proliferation of parents is a bit unfortunate. Any chance of easing the "one child layout cell per layout" rule in the future?
