The program is Quadrivio General Edit.
This is the ad I recalled from MacTech.
And here is an image from the last version:
As you can see, the system has a field where you type in stucts in C-like format on the right and it decompiled the data on the left. The templates appear to be stored in text format, parsed on load into the format you see.
The image ...
I'm going to put this up for now, although I'm still trying to find more info and I may be incorrect. It does not hit all of the buttons, I still seem to recall another app for this. But in the meantime, see if this rings a bell:
The app in question may be Resourcer. It was a common feature in MacTech (and others). It used a system of templates, stored in ...