OPML has served us well, but for OO4 I would like to see a File > Save > File Format > FoldingText

The FoldingText outline format (nesting fully-encoded in plain text with markdown and tab-indents, and columns/attributes encoded as @key(value) tags, is just so much more humanly useful and tractable than angle-bracketed XML, with all its opacities and fragilities.

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