[Fenris447]

So here's what I did:

The armor levels up, so I wanted to be able to easily make a new version with the extra bonuses at each level. I saw that Magic pieces like Armor of Invulnerability act as a modifier on a base piece of armor via a Gizmo. So I made a level zero, non-magical piece that has the tag to not generate proficiency. It's classified as heavy armor, with zero bonus to AC. I unchecked the disadvantage on Stealth.

Then I made a magic piece, based on one of those "modifier" type of heavy armors. It adds the +8 to AC. I then looked at Elven Chain to see how it grants automatic proficiency in itself; it's done through a Proficient Helper. I added that to the magic version. Then I made sure the magic version pointed at the base through the Gizmo.

By selecting the magic version on my character, I got everything I wanted. It applied +8 (total 18) to my AC, acted as if I was automatically proficient with it, and didn't give me disadvantage on Stealth. It's technically listed as Heavy Armor, but that classification now only serves to disable the DEX bonus. I can live with that, since in-game it really doesn't have any kind of classification at all.

When the armor levels, I'll just copy the magic version, name it "Defender Level 3" and add/tweak whatever new powers it provides. It will still refer to the base version to make sure I'm automatically proficient in it, not provide the DEX bonus, and not give me disadvantage on Stealth.

Let me know if none of that makes sense. Thank you, as always, to everyone here that regularly lend a helping hand and make this program even more amazing!