You either have to click on "class components" (above thecomponents list) so you can see all components of the ship; there you can remove them. Or you switch to "wide view" at the bottom, then you see race and class components next to each other.
Silly question but I am only browsing thru C while playing Aurora old. I see on ship design how you can add parts by clicking on left or right button on mouse but there seems to be no way to take parts off during design. thanks