A popup button widget with a non-anchored popup has the wrong alignment (seems to have extra top margin and act as if it is anchored even though the anchor is hidden)
It would also be great if we could physically align/place the popup so that its right edge aligns with its trigger/anchor right edge.
Floatable element supports this with "horizontalPosition: end" - and mw.rcfilters.ui.FilterItemHighlightButton (where this popup is from) passes that in, but it seems to be overridden in the popup.
