Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Default Size
PREF_MM_SIZEParameter: Shader Default Project
PREF_MM_SHSCENEParameter: Material Default Project
PREF_MM_MATSCENEParameter: Frame Rate (FPS)
PREF_MM_FRATEParameter: Preview Length (sec)
PREF_MM_PREVParameter: Node Preview Size
PREF_MM_NODE_PREVIEW_SIZEParameter: 3D Preview Scene
PREF_MM_NODE_MAT_PREVIEW_SCENEParameter: Preview HUD
PREF_MM_NODE_PREVIEWNAMEParameter: Default Material
PREF_MM_DEFAULT_MATERIALParameter: Always Open Node Editor
PREF_MM_ALWAYS_OPEN_NODE_EDITOR