How much training/experience do you have with Inventor?
I ask, because it is still unclear to me exactly what you want to accomplish.
Do you have an image or link to something similar to what you are trying to design?
In the following, I am going to assume that you have zero training/experience.
In Inventor you normally work as though you are making physical parts and physical sub-assemblies and assemblies.
That is, one part is one file.
One sub-assembly is a collection of parts put together by certain rules (Constraints limiting Degrees of Freedom).
On assembly is a collection of parts or sub-assemblies or parts and sub-assemblies (just like the real world).
My guess is that you are trying to model all of your parts in on part file, which can be done, but isn't a logical representation of the real world.
If you want to get the physical dynamics of real world assemblies - you will want to learn to follow real-world logic in the design of your parts, sub-assemblies and assemblies.
Once you gain experience, then you can "cheat" in the digital world with techniques like multi-body solids.
But for now, you should stick to duplication of the real world in your virtual design world.
1part=1file
As such, there is seldom a need to move a part (or feature) within a part.
Now this can by used in some powerful modeling techniques, but probably not for a beginner.
You move parts in an assembly (space), not in a part.
Logically moving a part in a part doesn't even make sense in the real world. I can't even think of an example where that is possible. Maybe a deformation forming process could be considered "moving a part in a part".
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