Found some new tricks.
In pumpkin gorge we can grab the white rune without fighting off the tentacles. When you get to the area, avoid the trigger that makes all that crap rise out of the ground and jump onto a pumpkin on any side. Dash jump towards the rune from there and you should just barely make it.
Also I found a pretty simple way to avoid a bunch of triggers. It turns out that a) nothing will trigger while the inventory window is on, and b) Dan still moves when set in motion before the window appears. Normally you can't turn on the inventory while Dan's speed is anything but 0, but pressing the select button twice while the inventory is displayed will close it and turn it back on after a second or so. During that second we're able to move and even then the inventory window will appear. I went through all the levels and found some use for this - mostly making the levels with known shortcuts even shorter by preparing the glitch, dropping down a ledge, and eventually avoiding a kill trigger where it wasn't possible before. I also found a spot where you can avoid a door-transition trigger by hitting a nearby wall with your sword and being pushed past the trigger, but it turned out to be a dead end.
Ok, here's a list of places where this trick works:
Cemetery hill:
You can get up the hill and drop down avoiding the kill trigger. You could drop to the middle of the gate with the witch talisman, so that you grab it and you're still able to get out. I doubt it would be faster than grabbing the club, then the talisman like you normally would, though.
The enchanted earth:
You can do start falling way sooner - as soon as you hit the second lift.
Pools of the ancient dead:
You can enter the void right after grabbing the last helmet. In real time I was able to at least skip the annoying battle that happens right after, but I'm sure you'll be able to fall straight on the boat when TASing.
The lake:
You can start falling right after you gain control over Dan - go straight for the exit.
The crystal caves:
I wasn't able to fall through the pit where the yellow rune is required, because of the platform at the bottom. There are a couple of small spots where you could fall through it, but the time window between closing and reopening the inventory screen was too small for me to be quick enough to reach them in real time - maybe you'll have better luck with frame advance in which case the whole level could be skipped. If not, we call start falling in the room where you summon the dragon, and go straight for the exit. I dunno if the latter would be faster than just rushing towards the exit normally, though.
The haunted ruins:
So now the route looks like this: 1) skip the damn chicken herding and immediately start falling towards the room with the the king's crown, 2) return the crown to the king, 3) skip the fight with the statues (finally), don't even flip the switch, and most certainly don't grab the green rune -
fall through here (the position is very precise, you have to just barely miss the ground, otherwise you'll end up on a solid kill trigger a couple of feet below) down to the catapult (you still have to flip the switch near it and board it, since it's the only way to trigger the exit).
The ghost ship:
You can start falling a bit earlier, near the red rune where the cannons are.
The time device:
You can start falling immediately after gaining control over Dan.
That's basically it. I was hoping for something... You know... New. I tried avoiding the water in return to the graveyard, alongside other levels, and falling straight to the boss fight, but it appears that the liquid pits in this game are only a couple feet deep, with solid ground underneath. I was also pretty certain that avoiding transition triggers which appear as holes/trap doors/whatever like the first one in the hilltop mausoleum, most of the inside the asylum ones, and the two in the asylum grounds, would allow us to enter the void in those levels, but all of those are, just like the liquid pits, just a few feet deep with solid ground underneath. I'll see if I can find anything else.