In the 1.43nc editor, trigger areas are only shown if you select Lemmix/Neolemmix as the style when opening a .lvl file. If you select Superlemmini as the style, they will not display. In any case, trigger areas work differently depending on the platform/engine, and if the traps function on Lemmix/NL, they should work on Superlemmini as well and hence no adjustment to the traps is needed. For example, in Lemmini the trap checks for the middle of the Lemming, while in Superlemmini, the traps check at the foot of the Lemming instead, and as has been mentioned at times, while the latter may seem odd, this is actually how trigger areas work on Dos/Amiga. Hence this explains why it's much harder to avoid traps on Lemmini but in contrast much easier to avoid on Superlemmini by, say, building over the trigger area.
I just checked Fun 9 and the same problem with the ghostbuster trap occurs there as well, where it is placed a pixel too high and hence doesn't work. Therefore, the trap not working on New Formats NL is simply due to the conversion preserving that. Makes sense, since the pack was originally for very old Formats NL.