Straight up let me say I don't have an answer for you. Second, if the rest of the site looks as good as that page...noice.

Now. You're right, you can't select multiple choices and, also, typing 'abba' into the 'open link' section will do nothing as that section tells the link how to open. Try choosing 'Same window (_top)'. It isn't what you're looking for, but it will show you what those choices do.

I'm curious if there's an answer myself. Nothing in the pipeline, but it would be interesting to file in the old memory box.