The format is somewhat open. Unity stores a lot in plain YAML files. Unreal has a wild serialization framework that is part of the freely accessible source cide

The format is somewhat open. Unity stores a lot in plain YAML files. Unreal has a wild serialization framework that is part of the freely accessible source cide (but tons of strings attached - so be careful!). So you might get some reuse out of these editors, but the catch is that they are extremely engine specific (with UE, I can't quite tell if the editor is built for the engine or the engine for the editor). So you'd just set yourself up to replicate the same engine design because it makes handling the output of these editors easier.