Key signature after intermediate double bar

Suppose in a hypothetical example that an intermediate double bar appears in the middle of a line, and the key changes from C minor to C major. Musescore won't let us insert accidentals except on a note, so how is it possible to define the key change in the first measure after the double bar? I suppose the first B, E, and A that occur after the double bar could have accidental naturals, but that isn't a very good solution, and adding a key signature of no sharps and no flats obviously has no visual effect. Am I missing something?