The Remove element tool renders a remove button at a given position above the element. It accepts a few additional arguments, which can be passed as an object to the element tool constructor:

x string | number Use percentage strings (e.g. '40%') to position the button relatively to the element width/height. A number means distance from the top-left corner of the element. Default is 0.
y
rotate boolean Should the button rotate according to the element angle around the element center? Default is false.
offset object Additional offset of the button from the position defined by x and y. Default is { x: 0, y: 0 }.
action function What should happen when the user clicks the remove button? Default: 
function(evt, elementView, toolView) {
    elementView.model.remove({ ui: true, tool: toolView.cid });
}
markup JSONMarkup The markup of the button, provided in the JointJS JSON format. Default is undefined (no content).

Example:

var removeButton = new joint.elementTools.Remove({
    focusOpacity: 0.5,
    rotate: true,
    // top-mid
    x: '50%',
    y: '0%',
    offset: { x: 10, y: 10 }
});