The Object Remover when enabled, will highlight any object with the Grid Object class attached to it presuming the Remove Preview Mat is assigned. The Object Placer adds this class automatically on object creation. When hovered over one of these objects, left-clicking will delete the objects themselves, and remove them from the Grid Square they are assigned to.

Remove Preview Mat

The material used to replace the hovered objects material.

Drag remove

This will enable you to click and drag over objects and remove them instead of clicking.