One or two examples for a sort of harmonic tremolo would be nice, I can't get the sound…

For the Vibrato algorithm, you may check out those factory presets in H9 Control. 

For the Harmodulator algorithm, you need to set the Pitch A and B to Unison, set the Mod Depth to a small value (like 30c or m2), and Shape parameter to SINE or TRIANGLE, then you should be able to get some harmonic tremolo sound.