Sketches added to planes that are in the same position end-up re-using any existing sketch plane on that plane, even if the existing sketch plane is hidden.
If a sketch plane that would otherwise be used is hidden, a new sketch plane should be created for the sketch.
We’ll support multiple overlapping sketch planes as we add history-based parametric modeling to the app. If you haven’t already, sign up for the beta to get early access to try it.