For it to be a true polychord the register has to be separate otherwise it becomes an added note voicing.
Obviously you can move the chord track to a melody and soloist channel and then transpose one of them by the requisite amount of semitones.

The other way which is one I do quite a lot isn't so much a polychord as an added note voicing which will give you the dissonance level but without the separation of register. (It's a moot point as to whether you hear a polychord as two distinct chords anyway or one large chord tied to the root)

to achieve it find the nearest voicing to the combined chord using an inversion over a bass note. Move it to a spare melody channel then use the 'low root' voicing in the melody harmony feature moved up an octave or to to add any missing note from the voicing. The problem with this is that you'll have to enter the note as a single note chord in a new chord sheet to get the melody harmony to add it, meaning a lot of cutting and pasting two sets of changes.

A third way is to find a really sparse left hand chord style that outputs only 3 or four notes max. Enter the first of your two chords and use the same method as above but this time use a 3 note melody harmony to get the other chord.

HTH

Alan