I've looked at the remaining unknown bytes (or bit flags, in some cases). Some of them really have no pattern, and we might have to observe closer. However, there's a lot that seem to be the same on all but a few levels.
I'm going to list a few groups of levels, that share currently-unknown values in the data with each other, but different from all levels outside the group. To be very clear - each group is independent. And I realise this is a long shot, but also figured it doesn't hurt to ask.
And just to be clear - it's entirely possible some (or even all) of these are just huge nothingburgers, possibly remnants from the official editor or of features that were removed in the final game, or something like that. So please don't spend too much effort on thinking of it - this is more a "if anything comes to mind, let me know".
Group 1: "Bounce Bounce", "Play Time"
Group 2: "A Shortcut Through The Forest", "Play Time", and all practice levels
Group 3: "This Is The Army", "Stilt Walkers" and "Let The Race Begin"
Group 4: "Alilemms", "Rescue Team" and "The Hanger"
Group 5: All enclosed levels, plus "The Prisoner" and "Claustrophobic" (these last two still have the cameras in enclosed areas, so perhaps it's some setting that relates to that..)
Group 6: "The Bean Machine", "A Shortcut Through The Forest", "Hole in Ten", "Fore!", "Lemlab", "Spaghetti Junction", "Ricochet", "Motherboard", "Birthday Cake", "Brechin's Staircase", "The Hanger", "The Catacombs", "Hole In One, Two, Three", and all practice levels
Group 7: "The Bean Machine", "Alpine Assault Course", "Alilemms", "Jelly Climber", "Oh No! More Pyramids!", "Garden Maze", "King Coder's Tomb", "Rescue Team", "The Arena", "Snake", "The Five Arches", "Brechin's Staircase", "Ski Jump", "Family Tree", "Raiders of the Lost Lemming", "Jelly Belly Islands", "Castle Peralus"
Group 8: "Attack Of The 50ft Lemmings", "Jelly Climber", "A Head Above The Rest", "Play Time", "The Arena", "T Minus 5 And Counting"
Group 9: "A Shortcut Through The Forest", "Stilt Walkers", and all practice levels
Group 10: "Bounce Bounce", "It's A Classic", "Lemlab", "Rescue Team" and "Tuther Circus Level" (with "Picky Platform" having a unique third value, instead of the same one as all other remaining levels)
Group 11: "The M-A-Z-E", "Rescue Team", "Team Work", "Death Slide" and "Slippery"
Group 12: "Alpine Assault Course", "Slippery Maze", "The M-A-Z-E", "Ski Jump" and "The Hanger"
Additionally, can anyone think of any attributes unique to any of the following levels?
- "Take A Dive"
- "Bounce Bounce"
- "Jelly Climber"
- "Lemlab" (other than the laser trap)