-In theory, you can output Midi CC via Arp, Midi CC Lfo, StepLine, on both of the higher levels.
This works on Program, but (at least for me) not on Layer level.
(eG Arp on layer level, choose CC9, draw some CC values, right-click on filter on KG level, Add modulation/External/CC9 > nothing works.)
Is this correct, or do I miss something?

-Another Modulation issue I have is the workaround of the3ug3reeder postet on your KVR FAQ pages. It’s about Re-triggering envelopes on Progr/Layer (https://www.kvraudio.com/forum/viewtopic.php?f=200&t=451038)

The workaround basically is creating a Multi envelope on Layer level (for a dummy osc) which can then modulate any parameter on Layer level.
In my experience, this doesn’t work at all.
The Multi envelope has the advantage that you can see if it’s been triggered – which it does, be it on Progr/Layer or KG level.
But the crucual point is the Mod destination, and this can only be on KG level, otherwise it won’t work.
At least here, so maybe please correct me if I’m wrong!