I'm using the same method used in CCAncients.net website.
I do prefer "date" ordered listing (keeping only one list), but I'm always open to new solution...
I'm used to separate scenarios with CODENAME so I'm going to explain it again:
- official scenarios have a CODE composed by a number representing expansion and a number representing progressive order, so base game scenarios code will all start with number "0" and Expansion 1 scenarios will start with 1, and so on... (ex: 001, 002, 101)
- unofficial scenarios have different caption that represent initial name/surname letter (ex: Michael Dippel scenarios will all start with "MD" as MD01 MD02 and so on).
Sadly there's no way to create "bold effect" only for specific scenarios... but "indentation" could be possible.