Hi Jo,
Welcome to the forum. We’re in exactly the same boat - I also have an oversized 10 kW Vaillant unit.
The hysteresis value for heating is a secondary mechanism. Normally, cycling is managed with the Compr. Start Heating and associated Energy Integral setting. If you reduce this value (say from -60°min to -100°min), you’ll get less cycling and longer cycles at the expense of potentially stronger indoor temperature swings. COP is barely affected by this setting, though I have the impression that the higher values (-30°min) have worse COP. There are lots of posts on the forum regarding the energy integral, e.g. here or here.
Normally, this mechanism will start/shut down a cycle before the default hysteresis kicks in. If you’re aiming for the longest cycles possible, set the Compr. Start Heating to -100°min and hysteresis to 10K to be safe, but even 7 should not have an impact.
Apart from that there’s nothing you can really do to tame an oversized unit. If you go through my post history you’ll find a number of posts with more background on this. I haven’t looked at those compressor modulation settings you mention, but my heat pump never goes above the minimum modulation anyways, except from a few minutes at the beginning of a cycle. We just have to live with it and be happy that the Vaillant heat pumps have a relatively smart way to prevent short cycling.