Newer versions of TestStand supports .NET 8. So now, instead of AppDomain, it is AssemblyLoadContext (ALC). By default, TestStand uses one ALC for all .NET code module execution and a separate ALC for edit time scenarios like module intellisense.
In next version of TestStand, we plan to have an opt-in feature where a step type can specify that all .NET modules related to that step type (code module, substeps, step settings pane) will be executed in a different ALC. We also intend to have the opt-in feature where a group of step types can specify that they want to use the same ALC.
