Jay opml export from Legend itself is not very compatible with its own opml importer… For one thing, a lot of the properties aren’t exported, because the “Include Prefixes” option in Export has no effect.
Beyond that, I can confirm that with even simple !
dates, in the OPML, the item has a date field like: <outline date="1638658800000" text="has a date Today " />
but on re-importing it, you just get the date as regular text. I couldn’t figure out how to manually edit the OPML so that it would import as a date.
There are a bunch of other things like that - bold, italic, and underlined text works as expected, but struck or highlighted text doesn’t, exported code blocks don’t re-import properly, and so on. I have a file of notes about it, including the formats for dates, tags, etc., but I haven’t posted it yet. If you’re interested I can. There’s so much I like about Legend, but broken or missing import/export functionality is the reason I’m not really using (or paying for) it… so I’d love to see it improved!