Library: Open = Open in a floating window reminded me of a Mac bug that I believe has been there as long as Logos for Mac has existed, but for which I'm not sure there has ever been a case filed:
1) Right-click on the Library icon.
2) Try out the options.
>> Open and Open In A Floating Window both open in a floating window. Open is supposed to open in a dropdown, like it does on Windows (see link above).