Hi, one of the things I really like about AC20 is the flexibility that the new property manager, and the ability to create almost any type of property gives us.
Here is an idea on how you can achieve what you want using the property manager.
1- you make a new property, in any convenient group, or do a new one, however you want, and you will use this property to write the truncate ID you want for any element.
2- then you add the truncate ID in the wall types. (I'll save it in the favorites, I wish AC have associative favorites in case of later changes)
3- After that just use any label that will let you call to this property to be labeled in a element, in the Pic I use "Identification and Property label 20"
PD: I though that we could give an ID to the composites, I just realize you can have ID only in the materials but not the full composite, it will probably be nice to have an ID for Composites too.