The Custom Wizard plugin does not currently do this unfortunately.
However, while I appreciate the reference to the Custom Wizard Plugin, I think it’s overkill in your case. I’ve made you a little theme component that achieves what you’re after.
https://github.com/paviliondev/extended-custom-field-description
Just pop your custom field name and your long description in the component’s setting (comma seperated) and bob’s your uncle.
