Ctrl + clicking a control resets it to what Serum considers its default value to be. The request is for Ctrl + Shift + clicking a control to reset it to the value saved in the loaded preset (if none is loaded, reset to Serum's default). This would be convenient as undoing is always sequential, and sometimes you want to reset a control which was tweaked long ago or during another session.
Serum 2.0.16