What function does the Custom Shape tool serve in graphic design?

The Custom Shape tool in graphic design is specifically designed to create unique and intricate vector shapes and design elements. By using this tool, designers can select from a variety of pre-defined shapes or create their own, which can enhance the visual appeal of a project with diverse graphics that align with their creative vision. This function allows for the incorporation of customized elements into a composition, facilitating a more personalized and distinctive design.

The other options refer to different functionalities within graphic design. Aligning text deals with positioning type elements within a design, modifying existing images pertains to alterations applied to photos or illustrations, and adjusting the size of layers involves scaling elements within a composition. Each of these serves a unique purpose, but none directly relate to the primary function of the Custom Shape tool.