Sets a paragraph-specific margin. Paragraphs are numbered starting with 0.
This method is experimental, and works reliably only when the paragraph is not marged or split. Merging or splitting a paragraph with margin settings causes the settings to be transfered unpredictably (although other paragraphs in the editor can be safely split or merged). If the last paragraph in an editor is empty, settings assigned to that last paragraph are ignored.
The first line of the paragraph is indented by first-left points within the editor. If the paragraph is line-wrapped (when the editor has a maximum width), subsequent lines are indented by left points. If the editor has a maximum width, the paragraph's maximum width for line-wrapping is right points smaller than the editor's maximum width.