You can create your macros in My Settings. then when you're responding to a users you'll see macros in top right corner of your window.
You can select that macro and the text will be autofilled to your response. It just adds the text like a form letter. It does not automatically submit like the Needs Details buttons.
I believe (though not certain) this platform is built on the Lithium platform so you could search around on the Lithium platforms for Macro functionality.
Just to be clear, this has no relation to a SAS macro. Macro is a generic term to define: a single instruction that expands automatically into a set of instructions to perform a particular task. (from dictionary).