[Spectrasonics Trilian Mac Download
Sharif Garmon
As the OP noted, the problem is that Trilian has no key switch for playing "normally" - only for decorative articulations like slides or staccato. Once you've played a different articulation, it's not clear how to get Logic's articulation switcher to tell it go back to the normal sound.
Here's a really good vid on the subject. There's "inverted" key switching (a list of all 7 others) on the "default" to turn it off when another one is chosen (otherwise they both will sound) - It sounds like your solution is good, but better if you add it to its existing list of inverted switches. When there's more than one assignment to the first part, the first part doesn't show any, but if you right-click on it you can edit the list and add a positive Key Switch as well. If you were playing it "live," the Note Off should revert it automatically, but it seems like Logic's Articulation Sets might not act the same as doing it with a keyboard.
Here's an article that explains how to use Trilian with Articulation sets.
The trick is to reassign keyswitches in the Trilian Live screen - clear em out and re-do them all... but use Logic's Editor>Piano Roll keyboard to enter the pitches. No Inverse Keyswitches needed.. they're for live players or recording a performance into Logic. As soon as you activate an Articulation set, you're screwed without fixing the keyswitches.
-up-spectrasonics-trilian-for-use-with-articulation-sets-in-logic-pro-x/