I’ll give my initial thoughts, maybe they can be built upon…
You might use a layout like my Sidebar Tabs Ledger with columns of checkboxes for each area of the spec that needs to be covered.
Checking a box would add the spec area value to a field “spec-covered” in the top-level tiddler. The checkboxes in listfield mode should be able to show as checked as soon as the related spec value is added to the list field.
Add a class name to a container that wraps each list that makes a level of the hierarchy. The CSS classes would handle indenting and bullets instead of using wikitext.
Each list item would use the same template to display the checkboxes, with the checkboxes adding values to the specified field in the top-level tiddler.
Edit: having a single line at the top and/or bottom of the top-level tiddler with the same row of checkboxes can be used as a master checklist of the spec areas so that you won’t have to keep scanning each column to track the areas covered.