I'm familiar with the scratch and current workspace parameters...what I need to be able to do, is have a tool, let's say something as simple as "Create Feature Class" run against the default project geodatabase, without the user having to identify where or what that geodatabase is. Example, a user creates a new project in C:\GIS\USERNAME\SASQUATCH\2018, and the default geodatabase that is created when the project is created is named "MyProject2039.gdb", when the user opens the custom tool I've made, the only choice they have is what to name the feature class. The creation of the feature class will default to MyProject2039.gdb. Currently I'm not able to do that in Pro model builder with scratch or current.