I have this cylinder and want to sketch a pattern at the end and revolve it.

For this I would like a plane similar to Plane 5 but at a 90 degree angle, so that it cuts through the center axis of my cylinder.

I'm having trouble properly referencing geometry, as can be seen in the top left corner (a plane off which Plane 5 is referenced because I couldn't find any other way to create a plane tangent to this round shape).