Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Download Location
PREF_BROWSER_DOWNLOAD_LOCATION
Parameter: Clear Downloaded
PREF_BROWSER_CLEAR_DOWNLOADED
Parameter: \u27F3
PREF_BROWSER_RECALCULATE_SIZE
Parameter: Show Unavailable
PREF_BROWSER_SHOW_UNAVAILABLE
Parameter: Preview Width
PREF_BROWSER_PREVIEWWIDTH
Parameter: Preview Height
PREF_BROWSER_PREVIEWHEIGHT
Parameter: Projects as Watch Folders
PREF_BROWSER_WATCHFOLDER_AUTOMOUNT_DOCUMENTS