Selecting bearings based on needs
Editing components created by design accelerators
Modifying sheet metal parts
The design accelerators exist for one reason: design. As powerful as Inventor is, most of what you've been doing to this point is modeling, and any 3D system should be able to model parts. Design is a different issue. Design means using engineering calculations to determine the correct component for the job rather than hoping you have it right.
The geometry of a part is the solution, not the question; so although tools like finite element analysis are still the best solution for creating custom parts, using time-tested data to find which ...