At the Transclusion dialog, after a click or double-click on the chosen parameter, nothing happens. Is the user expected to click on the "Add parameter" label at the top? To press Enter? To read the user guide for instruction on how ? None of these steps help.
This is a usability bug - the actual button is hidden below the fold, at the end of a very long list that is not intended to be scrolled through, and thus hard to discover. The button should be always visible in the dialog - otherwise, the dialog becomes unusable with long lists of parameters.