Your environment might have different versions of Identity Manager.
If you configured and wrote policies for an earlier version of Identity Manager in your environment, you might encounter the following issues:
You could easily build a solution that would not deploy.
You did not know which features worked in one environment versus another environment.
To solve these issues, Designer tracks versions of the following objects:
Identity Manager engines
Identity Vaults (trees)
Drivers
As you use Designer, you see only the user interface of features that apply to the version that you are working on. Project Checker and Deploy ensure that what you have configured is supported in the target environment.