Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Default Size
PREF_MM_SIZE
Parameter: Shader Default Project
PREF_MM_SHSCENE
Parameter: Material Default Project
PREF_MM_MATSCENE
Parameter: Frame Rate (FPS)
PREF_MM_FRATE
Parameter: Preview Length (sec)
PREF_MM_PREV
Parameter: Node Preview Size
PREF_MM_NODE_PREVIEW_SIZE
Parameter: 3D Preview Scene
PREF_MM_NODE_MAT_PREVIEW_SCENE
Parameter: Preview HUD
PREF_MM_NODE_PREVIEWNAME
Parameter: Default Material
PREF_MM_DEFAULT_MATERIAL
Parameter: Always Open Node Editor
PREF_MM_ALWAYS_OPEN_NODE_EDITOR