Hello Jeff,
Sorry if I misunderstood your problem and/or level of your proficiency.
You could create a groove into cylinder by creating profile curve, then revolving it around the axis (Revolve command) to create solid which can be subtracted from the cylinder afterwards (BooleanDifference command).
See attached image and Rhino file.
Untitled.3dm (258.3 KB)
Please explain further if needed.
Best,
Jonas