Does Gimp have any kind of smart object equivalent yet? I've been using Photoshop for years and haven't been able to move to Gimp because it's missing a lot of "non-destructive" editing features like smart objects, smart filters, adjustment layers, etc.
Not that I'm aware of. The workflow would be to make a copy of the thing before you do a destructive operation on it. You can put it in a hidden layer or something.