So my question is as follows, is it possible to move an actor inside the system boundary of a use case diagram? Can it be a part of the system.
I set a server as an actor, in where a customer interacts with the server in an e-commerce environment. Is it possible or should I move the server inside of the system? Since the server is a part of the system that the customer is interacting with.
This server is most likely then going to be used by an admin role.
No, you can't do that, unless you model only a part of the system.
By definition an actor is external to the system. It can be a user, other system or a sensor.
If you want to show a system decomposition into smaller parts, use component diagram.
Note, the role of a use case diagram is to show functions of the system as a whole.
On the other hand you may depict just one part of the system (ie. system tier). In such case other parts (tiers) are external to the modeled system part under consideration.