What am I talking about? The associate global parameters (AGP) button that now appears next to many instance and type parameters in Revit. AGP is a nice feature, introduced in the Revit 2016 Release 2 update, they allow us to associate parameters in the project environment, allowing us to make global parametric changes. You can see this knowledge network article here to learn more.
Where I see it causing problems for users is when trying to change the material of objects. You can't actually see the material browser button until you click in the cell. So naturally, users click on what they can see, which now happens to be the AGP button.
When you click this button, the AGP dialog box opens and users are left scratching their heads. (I have even seen some students attempt to search for the material in this dialog).
What you really need to be looking for are those 3 little dots next to the material name. As I mentioned before, you can't actually see this button until you click in the material cell. If you know where it is, you can actually just click in this spot, the button shows and opens the material browser.