I want the opening window to look like this in core only.

[LeeJaeYoung]

wall is this

it is "Rectangular Window Opening 25"

in core only

I want it to be expressed like this. (in core only)

[DGSketcher]

See if the MVO settings for Construction Element Options and Detail Level of Door, Window... can deliver what you need. You may get it just by changing the CEO > Window to Show opening only. You may also need to create and save the settings to a new MVO.

[LeeJaeYoung]

In the Entire Model, it is correct to express even the finish.
In core only, it should be displayed only on the structure, but I am telling you that it is expressed until the invisible finish.

[LeeJaeYoung]

The problem here is that the wall is designated as Outline in order to avoid the cut plan of the wall.
Raising the height of the cut plane has the same problem.

In my opinion, it is not.
If this wall is not expressed as an elevation line on the plane, there is no problem.

I used window opening to wrap the finish on the opening part of the wall...

The whole has to be the facade, so it seems like this part should be cut as 

Barry Kelly taught.

Solved: I'm trying to drill a hole in the railing wall. - Graphisoft Community