You're importing a single tiddler, not an entire plugin.
It doesn't matter what preview is used.
Just press "import" and then a tiddler should appear with the name of the imported tiddler. Click on the name to navigate to the imported tiddler.
You might want to change the name of the tiddler since it is no longer part of a plugin and since, as a system tiddler ($:/...) it will be hidden from the "recent" list.
Good luck