If you really want to understand this option string, refer to the method ScImportOptions::BuildString() in the source code file /core/sc/source/ui/dbgui/imoptdlg.cxx
https://opengrok.libreoffice.org/xref/core/sc/source/ui/dbgui/imoptdlg.cxx
And best link to the current and latest CSV filter options help that meanwhile (24.2) knows some new options.