Showcase is just a set of tools; they can be used (or misused!) however you want.
For example, if you don't play to a click, but your drummer is rock solid, you could place intros, outros, interstitials, sound effects, backing vocal parts, etc. onto the stems. In your DAW, remove most empty space between them. After loading into a Showcase song, place marker flags at the beginning of each audio part and turn Pause at Marker on. Then when that section of the song comes in, just press play—whatever you have recorded will play and will pause when it reaches the next maker, waiting for you to press Play again (or the drummer can strike a trigger). It now becomes sort of a sample player with sequential groups of up to 8 samples that can all be flied in at the press of a switch.
There are all sorts of other workflows as well. We'll be outlining some of them in the coming months