This idea is to add internal prerequisites within modules based on completion of all the activities under headers used to subdivide the module.
In some cases sequential completion of individual activities within a module is not required, but it is necessary to complete one group of activities before the next. If headers could be used to set the contents of the first header as prerequisites for accessing the content under other headers, then this could be accomplished without unnecessarily requiring sequential order for the entire module. Similarly, if it was necessary to complete the contents of the first three headers (in any order) before accessing the activities under the final header, those three headers could all be set as prerequisites for the final header.
This idea would also allow module requirements to be set separately for activities in each of the groups produced by the headers that subdivide activities in the module.
Some activities need to be completed in sequential order, while others may be started by students out of order. Allowing module requirements to be subdivided by headers, would allow the activities under some headers to require sequential order, while activities under other headers could proceed in any order.
I imagine it looking something like this:
