It may happen with other types of triggers, but I haven't tested all of them.
Basically, no combination of flags (that I've tried at least) make it so that you have to step on multiple combos before the secrets are triggered. Also, the secret sound isn't played when a step combo triggers them.
Link to demo: http://ifile.it/lz65bfd/multibomb.qst
(Ignore the first room and head right. I thought the same was happening with the bomb triggers, but I figured that one out.)
"Step triggers" are combos, not triggers.
Triggers = Trigger Combo Flags.
While "Step->Secrets" combos do in fact trigger Screen Secrets, they aren't capital-T Triggers.
No way to pull this off without scripts then?
The only way to do this is using tiered secrets, which leaves you with the following limitations:
1. You still can't use Hit All Triggers
2. The combos must be hit in a specific order.
Basically, have the first trigger be a normal trigger combo. Then, in the spot where you want the second trigger, put Secret Flag 16.
Next, on the Secret Combo dialog, set Secret Combo 16 to be another trigger. Also, set up the secret result combos as normal. But, using even more secret combos, you need to set normal, non-secret combos that correspond to the places on the map where the secret will appear. And, you need to set the flags on the secret combo to the be secret flag of the result (Ctrl-Click, I believe).
Since that's a garbled mess, I will give a specific example. Let's say you want two triggers to make a torch light, by stepping left and the right of the torch.
First, you place the trigger and the unlit torch on the map. The trigger goes to the left of the torch. The spot to the right of the torch gets Flag #16, while the torch itself gets #17.
In the secret combo dialog, you set the second trigger in spot #16, an unlit torch in #17, and a lit torch in #18. You set the flag on #17 to #18.
When Link steps on the left trigger, two things happen:
1. The second trigger appears (via #16)
2. The unlit torch is replaced with another unlit torch, marked with flag #18 (via #17)
Then, when Link steps on the right trigger, the unlit torch is replaced again with a lit torch.
It's possible to even longer, but you'll find that you quickly run out of secret combos, so for anything more complex, you probably want a script (or, tricky multiple-room trickery)