Ok, so then you just want to use pure MIDI, and *not* the controller assignment system at all.
You do not use controller assignments, you record the knob movements as MIDI data, and use the plugin's own MIDI learn system - I think that's what you are saying above...
Yes, you haven't correctly learned a controller assignment for the plugin parameter, you've only, presumably mistakenly, learnt to open the controller assignments window.
It doesn't really matter what you use to send MIDI CC's, anything that is a generic controller will work fine.
I don't use those, but there are a lot of them around. CH was recommending this one recently:
https://ghostnoteaudio.uk/products/conductor
I'm not sure why you'd need MIDI transform, unless there is no way to change the CC messages the controller sends (but this shouldn't matter with the plugin MIDI learn anyway, it will just learn whatever message that fader sends.)