If you (accidentally) create some double entry in Custom Window you can't select it. Both of them will be selected, but the buttons ("remove", "move up", "move down") control only the upper entry. So it makes impossible to delete accidentally created entry at the bottom.

Well, in the meantime you can delete the top one and then move the bottom one to where you want it. But I guess we should make it so that you can't add the same info item to a window twice.

This might be crazy, but maybe someone might want to have the information up in two places in the window? A more permissive design would be to make it so that only one of the copies is selected at a time, though I'm not sure if it's necessarily the easier option depending on how you generate items on that list.

OK, fixed all weirdness with duplicate items in 3635558. You can add duplicate items if you want, and then select them normally without selecting multiple items at once.

Try it out in the next release; I'll close this now.