I’d appreciate it, if you could rephrase what you said with a bit more clarity and explanation.
What exactly should I do to go back and forth between presets without having Halion switch instruments? And without having to resort to manual clicking, double clicking or using arrow keys + enter.
Also, why does it take longer to load a preset if I use the arrow buttons on the VST…

…as opposed to use arrow key keys + enter or double click presets in the Media panel?
Update: I tried every other Steinberg (stand-alone) VST. Padshop, Retrologue, The Grand, Backbone and even Groove Agent. These hotkeys…

…work without any problem. I can go back and forth between presets using these hotkeys and they load fast.
The only problem is Halion:
So let’s say I load Dark Planet in Halion and pick a first preset belonging to Dark Planet. Then I press Next (Preset) hotkey. It does not take the next Dark Planet preset but it picks a next preset in the ALL section:
So, I don’t know if I am overthinking this, but it would have been nice if I could browse presets using single keys. Not taking my mouse cursor to the next preset and double clicking, not pressing Down and Enter. But one single key. That way I could easily browse between presets in a particular library like Dark Planet, and then I could bind those single hotkeys to any USB device (a game controller, Elgato Streamdeck, a Tourbox, etc.) without me having to go back and forth between my stationary MIDI Keyboard and my PC. I hope this makes sense.
Also, I appreciate you trying to help, but a couple of screenshots would be nice. You call them ‘Preset Management’ and ‘Preset Browser’ - I don’t have anything to connect those words to. Cubase and Halion interface is a jungle. That is why I need something visual to refer to.