Sooner or later you'll find a model that's almost what you want. You're after sales orders, there's a DP: Sales Order model sitting right there in the list, you open it to make a small change, and the form won't let you. The model is read-only, and a message tells you it belongs to a content pack. That isn't a permissions glitch. It's the product steering you toward the right move, which is to clone the model and change the copy.

This article is about why that's the pattern, what a clone actually hands you to start from, and where the real work happens once you have one.