Yes, if it was that simple. I have a lot of other assemblies in this project that depends on this one and I would have to remove them all to do this. Anyways I have tested now installing it in to completely new unity project, Unity version 2019.3.13f1, and I get this when I press on Create ASMDEF button: After ok comes this: Not sure if these messages are supposed to come up or is something wrong. This is also free version of DoTween, I do not have paid one. Also if I press "Apply" button here this error comes up, after installation is done in empty new project. So it feels like a unknown assembly error I was showing you before realates with these issues.