How to import RTF file with indents instead of tabs?

I have RTF outline files (exported from Circus Ponies Notebook) where each outline level has its paragraph indentation set farther to the right, rather than having tab characters per outline level as OO requires. So I’m not able to import them. (I know I could use OPML, but then all bold/italic/etc. formatting is lost).

Does anyone know of a way to convert paragraph ruler indents to one or more tabs?