Custom Activity with existing activities inside

I’m trying to create a custom activity, which will acts as a scope (so that it can contain other activities).

The idea is that it is essentially a custom “Use Application/Browser” activity which will take more specific launch parameters. I have used the Visual Studio extension to create an Activity that will take the two arguments “Language” and “Company” which will be used in the launch parameters like: “application -company=COMPANY -language=LANGUAGE”

What I cannot figure out is how to implement the already existing “Use Application/Browser” activity inside my custom Activity, and make it use my custom parameters.

I tried to look at other similar questions, but they implement “UiPath.Core…” but I can only find “UiPath.Shared…”, I’m lost here.