You can switch to Concordance Results window with [Ctrl]+[Tab], you can choose source/target segment with [F6] to select needed text.
Then you can use [Ctrl]+[Alt]+[F3] to have preselected text inserted into active segment at cursor position.
That is not as easy as [Ctrl]+[1], [Ctrl]+[2], [Ctrl]+%whatever% … , but concordance search doesn't return matches anyway - it returns just search results.