outline numbering

Tools|Outline Numbering|Paragraph Style always has ‘none’ for levels 1,2 and 3. I can modify those to Heading1,2,and 3 to make those headings appear in Navigator, but those modifications aren’t saved with the document. I have to do it again every time I open the document.

It seems to happen all the time with .rtf documents (the headings disappear after reopening the document).
It also happens with .odt documents, although in this case the headings show up in Navigator anyway.

Any idea how to make my changes persist, at least for a given document?